diff --git a/exercises/enums/enums1.rs b/exercises/enums/enums1.rs
index 511ba740..8d6602fa 100644
--- a/exercises/enums/enums1.rs
+++ b/exercises/enums/enums1.rs
@@ -6,6 +6,10 @@
 #[derive(Debug)]
 enum Message {
     // TODO: define a few types of messages as used below
+    Quit,
+    Echo,
+    Move,
+    ChangeColor
 }
 
 fn main() {
diff --git a/exercises/enums/enums2.rs b/exercises/enums/enums2.rs
index 18479f87..4c454a71 100644
--- a/exercises/enums/enums2.rs
+++ b/exercises/enums/enums2.rs
@@ -6,6 +6,10 @@
 #[derive(Debug)]
 enum Message {
     // TODO: define the different variants used below
+    Move {x:i32, y:i32},
+    Echo(String),
+    ChangeColor(i32, i32, i32),
+    Quit
 }
 
 impl Message {
diff --git a/exercises/enums/enums3.rs b/exercises/enums/enums3.rs
index 55acf6bc..3a04c771 100644
--- a/exercises/enums/enums3.rs
+++ b/exercises/enums/enums3.rs
@@ -6,6 +6,10 @@
 
 enum Message {
     // TODO: implement the message variant types based on their usage below
+    ChangeColor((u8, u8, u8)),
+    Echo(String),
+    Move(Point),
+    Quit
 }
 
 struct Point {
@@ -38,6 +42,12 @@ impl State {
 
     fn process(&mut self, message: Message) {
         // TODO: create a match expression to process the different message variants
+        match message {
+            Message::ChangeColor(color_tup) => self.change_color(color_tup),
+            Message::Echo(string) => self.echo(string),
+            Message::Move(pos) => self.move_position(pos),
+            Message::Quit => self.quit()
+        }
     }
 }
 
diff --git a/exercises/error_handling/errors1.rs b/exercises/error_handling/errors1.rs
index bcee9723..db87ed27 100644
--- a/exercises/error_handling/errors1.rs
+++ b/exercises/error_handling/errors1.rs
@@ -7,12 +7,12 @@
 
 // I AM NOT DONE
 
-pub fn generate_nametag_text(name: String) -> Option<String> {
+pub fn generate_nametag_text(name: String) -> Result<String, String> {
     if name.is_empty() {
         // Empty names aren't allowed.
-        None
+        Err("`name` was empty; it must be nonempty.".into())
     } else {
-        Some(format!("Hi! My name is {}", name))
+        Ok(format!("Hi! My name is {}", name))
     }
 }
 
diff --git a/exercises/error_handling/errors2.rs b/exercises/error_handling/errors2.rs
index 1cd8fc66..d152720d 100644
--- a/exercises/error_handling/errors2.rs
+++ b/exercises/error_handling/errors2.rs
@@ -25,8 +25,10 @@ pub fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
     let processing_fee = 1;
     let cost_per_item = 5;
     let qty = item_quantity.parse::<i32>();
-
-    Ok(qty * cost_per_item + processing_fee)
+    match qty {
+        Ok(value) => Ok(value * cost_per_item + processing_fee),
+        _ => qty
+    }
 }
 
 #[cfg(test)]
diff --git a/exercises/error_handling/errors3.rs b/exercises/error_handling/errors3.rs
index a2d2d190..5da5bbda 100644
--- a/exercises/error_handling/errors3.rs
+++ b/exercises/error_handling/errors3.rs
@@ -8,7 +8,7 @@
 
 use std::num::ParseIntError;
 
-fn main() {
+fn main()-> Result<(), ParseIntError>{
     let mut tokens = 100;
     let pretend_user_input = "8";
 
@@ -20,6 +20,7 @@ fn main() {
         tokens -= cost;
         println!("You now have {} tokens.", tokens);
     }
+    Ok(())
 }
 
 pub fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
diff --git a/exercises/error_handling/errors4.rs b/exercises/error_handling/errors4.rs
index 0efe8ccd..376ff508 100644
--- a/exercises/error_handling/errors4.rs
+++ b/exercises/error_handling/errors4.rs
@@ -15,6 +15,11 @@ enum CreationError {
 impl PositiveNonzeroInteger {
     fn new(value: i64) -> Result<PositiveNonzeroInteger, CreationError> {
         // Hmm...? Why is this only returning an Ok value?
+        if value < 0 {
+            return Err(CreationError::Negative)
+        }else if value == 0 {
+            return Err(CreationError::Zero)
+        }
         Ok(PositiveNonzeroInteger(value as u64))
     }
 }
diff --git a/exercises/error_handling/errors5.rs b/exercises/error_handling/errors5.rs
index 2ba8f903..f31e13f5 100644
--- a/exercises/error_handling/errors5.rs
+++ b/exercises/error_handling/errors5.rs
@@ -23,7 +23,7 @@ use std::fmt;
 use std::num::ParseIntError;
 
 // TODO: update the return type of `main()` to make this compile.
-fn main() -> Result<(), Box<dyn ???>> {
+fn main() -> Result<(), Box<dyn error::Error>> {
     let pretend_user_input = "42";
     let x: i64 = pretend_user_input.parse()?;
     println!("output={:?}", PositiveNonzeroInteger::new(x)?);
diff --git a/exercises/error_handling/errors6.rs b/exercises/error_handling/errors6.rs
index 1306fb03..d0c74107 100644
--- a/exercises/error_handling/errors6.rs
+++ b/exercises/error_handling/errors6.rs
@@ -25,6 +25,9 @@ impl ParsePosNonzeroError {
     }
     // TODO: add another error conversion function here.
     // fn from_parseint...
+    fn from_parseint(err: ParseIntError) -> ParsePosNonzeroError {
+        ParsePosNonzeroError::ParseInt(err)
+    }
 }
 
 fn parse_pos_nonzero(s: &str)
@@ -32,7 +35,7 @@ fn parse_pos_nonzero(s: &str)
 {
     // TODO: change this to return an appropriate error instead of panicking
     // when `parse()` returns an error.
-    let x: i64 = s.parse().unwrap();
+    let x: i64 = s.parse().map_err(ParsePosNonzeroError::from_parseint)?;
     PositiveNonzeroInteger::new(x)
         .map_err(ParsePosNonzeroError::from_creation)
 }
diff --git a/exercises/functions/functions1.rs b/exercises/functions/functions1.rs
index 03d8af70..841f86ce 100644
--- a/exercises/functions/functions1.rs
+++ b/exercises/functions/functions1.rs
@@ -3,6 +3,9 @@
 
 // I AM NOT DONE
 
+fn call_me() {
+    print!("hello world!");
+}
 fn main() {
     call_me();
 }
diff --git a/exercises/functions/functions2.rs b/exercises/functions/functions2.rs
index 7d40a578..5a251c3e 100644
--- a/exercises/functions/functions2.rs
+++ b/exercises/functions/functions2.rs
@@ -7,7 +7,7 @@ fn main() {
     call_me(3);
 }
 
-fn call_me(num:) {
+fn call_me(num:u32) {
     for i in 0..num {
         println!("Ring! Call number {}", i + 1);
     }
diff --git a/exercises/functions/functions3.rs b/exercises/functions/functions3.rs
index 3b9e585b..d3005ecb 100644
--- a/exercises/functions/functions3.rs
+++ b/exercises/functions/functions3.rs
@@ -1,10 +1,8 @@
 // functions3.rs
 // Execute `rustlings hint functions3` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 fn main() {
-    call_me();
+    call_me(5);
 }
 
 fn call_me(num: u32) {
diff --git a/exercises/functions/functions4.rs b/exercises/functions/functions4.rs
index 65d5be4f..95e63c39 100644
--- a/exercises/functions/functions4.rs
+++ b/exercises/functions/functions4.rs
@@ -14,7 +14,7 @@ fn main() {
     println!("Your sale price is {}", sale_price(original_price));
 }
 
-fn sale_price(price: i32) -> {
+fn sale_price(price: i32) -> i32{
     if is_even(price) {
         price - 10
     } else {
diff --git a/exercises/functions/functions5.rs b/exercises/functions/functions5.rs
index 5d762961..5fa8278c 100644
--- a/exercises/functions/functions5.rs
+++ b/exercises/functions/functions5.rs
@@ -9,5 +9,5 @@ fn main() {
 }
 
 fn square(num: i32) -> i32 {
-    num * num;
+    num * num
 }
diff --git a/exercises/intro/intro1.rs b/exercises/intro/intro1.rs
index 45c5acba..242db8ef 100644
--- a/exercises/intro/intro1.rs
+++ b/exercises/intro/intro1.rs
@@ -9,8 +9,6 @@
 // when you change one of the lines below! Try adding a `println!` line, or try changing
 // what it outputs in your terminal. Try removing a semicolon and see what happens!
 
-// I AM NOT DONE
-
 fn main() {
     println!("Hello and");
     println!(r#"       welcome to...                      "#);
diff --git a/exercises/intro/intro2.rs b/exercises/intro/intro2.rs
index efc1af20..8ee82d6a 100644
--- a/exercises/intro/intro2.rs
+++ b/exercises/intro/intro2.rs
@@ -5,5 +5,5 @@
 // I AM NOT DONE
 
 fn main() {
-    println!("Hello {}!");
+    println!("Hello {}!","world");
 }
diff --git a/exercises/move_semantics/move_semantics1.rs b/exercises/move_semantics/move_semantics1.rs
index aac6dfc3..a636de7d 100644
--- a/exercises/move_semantics/move_semantics1.rs
+++ b/exercises/move_semantics/move_semantics1.rs
@@ -6,7 +6,7 @@
 fn main() {
     let vec0 = Vec::new();
 
-    let vec1 = fill_vec(vec0);
+    let mut vec1 = fill_vec(vec0);
 
     println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
 
diff --git a/exercises/move_semantics/move_semantics2.rs b/exercises/move_semantics/move_semantics2.rs
index 64870850..db66c01a 100644
--- a/exercises/move_semantics/move_semantics2.rs
+++ b/exercises/move_semantics/move_semantics2.rs
@@ -7,7 +7,7 @@
 fn main() {
     let vec0 = Vec::new();
 
-    let mut vec1 = fill_vec(vec0);
+    let mut vec1 = fill_vec(&vec0);
 
     // Do not change the following line!
     println!("{} has length {} content `{:?}`", "vec0", vec0.len(), vec0);
@@ -17,8 +17,8 @@ fn main() {
     println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
 }
 
-fn fill_vec(vec: Vec<i32>) -> Vec<i32> {
-    let mut vec = vec;
+fn fill_vec(vec: &Vec<i32>) -> Vec<i32> {
+    let mut vec = vec.to_vec();
 
     vec.push(22);
     vec.push(44);
diff --git a/exercises/move_semantics/move_semantics3.rs b/exercises/move_semantics/move_semantics3.rs
index eaa30e33..b5e4db29 100644
--- a/exercises/move_semantics/move_semantics3.rs
+++ b/exercises/move_semantics/move_semantics3.rs
@@ -17,7 +17,7 @@ fn main() {
     println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
 }
 
-fn fill_vec(vec: Vec<i32>) -> Vec<i32> {
+fn fill_vec(mut vec: Vec<i32>) -> Vec<i32> {
     vec.push(22);
     vec.push(44);
     vec.push(66);
diff --git a/exercises/move_semantics/move_semantics4.rs b/exercises/move_semantics/move_semantics4.rs
index 99834ec3..acc76024 100644
--- a/exercises/move_semantics/move_semantics4.rs
+++ b/exercises/move_semantics/move_semantics4.rs
@@ -7,9 +7,7 @@
 // I AM NOT DONE
 
 fn main() {
-    let vec0 = Vec::new();
-
-    let mut vec1 = fill_vec(vec0);
+    let mut vec1 = fill_vec();
 
     println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
 
@@ -20,7 +18,7 @@ fn main() {
 
 // `fill_vec()` no longer takes `vec: Vec<i32>` as argument
 fn fill_vec() -> Vec<i32> {
-    let mut vec = vec;
+    let mut vec = Vec::new();
 
     vec.push(22);
     vec.push(44);
diff --git a/exercises/move_semantics/move_semantics5.rs b/exercises/move_semantics/move_semantics5.rs
index 36eae127..4c65cfb2 100644
--- a/exercises/move_semantics/move_semantics5.rs
+++ b/exercises/move_semantics/move_semantics5.rs
@@ -8,8 +8,8 @@
 fn main() {
     let mut x = 100;
     let y = &mut x;
-    let z = &mut x;
     *y += 100;
+    let z = &mut x;
     *z += 1000;
     assert_eq!(x, 1200);
 }
diff --git a/exercises/move_semantics/move_semantics6.rs b/exercises/move_semantics/move_semantics6.rs
index eb52a848..f8cef7f0 100644
--- a/exercises/move_semantics/move_semantics6.rs
+++ b/exercises/move_semantics/move_semantics6.rs
@@ -7,19 +7,19 @@
 fn main() {
     let data = "Rust is great!".to_string();
 
-    get_char(data);
+    get_char(&data);
 
-    string_uppercase(&data);
+    string_uppercase(data);
 }
 
 // Should not take ownership
-fn get_char(data: String) -> char {
+fn get_char(data: &str) -> char {
     data.chars().last().unwrap()
 }
 
 // Should take ownership
-fn string_uppercase(mut data: &String) {
-    data = &data.to_uppercase();
+fn string_uppercase(mut data: String) {
+    data = data.to_uppercase();
 
     println!("{}", data);
 }
diff --git a/exercises/standard_library_types/arc1.rs b/exercises/standard_library_types/arc1.rs
index 93a27036..b62df8e5 100644
--- a/exercises/standard_library_types/arc1.rs
+++ b/exercises/standard_library_types/arc1.rs
@@ -26,11 +26,11 @@ use std::thread;
 
 fn main() {
     let numbers: Vec<_> = (0..100u32).collect();
-    let shared_numbers = // TODO
+    let shared_numbers = Arc::new(numbers); // TODO
     let mut joinhandles = Vec::new();
 
     for offset in 0..8 {
-        let child_numbers = // TODO
+        let child_numbers = shared_numbers.clone();// TODO
         joinhandles.push(thread::spawn(move || {
             let sum: u32 = child_numbers.iter().filter(|n| *n % 8 == offset).sum();
             println!("Sum of offset {} is {}", offset, sum);
diff --git a/exercises/strings/strings1.rs b/exercises/strings/strings1.rs
index 0de86a1d..93086fea 100644
--- a/exercises/strings/strings1.rs
+++ b/exercises/strings/strings1.rs
@@ -9,6 +9,6 @@ fn main() {
     println!("My current favorite color is {}", answer);
 }
 
-fn current_favorite_color() -> String {
+fn current_favorite_color() -> &'static str {
     "blue"
 }
diff --git a/exercises/strings/strings2.rs b/exercises/strings/strings2.rs
index 0c48ec95..3a33ad13 100644
--- a/exercises/strings/strings2.rs
+++ b/exercises/strings/strings2.rs
@@ -13,6 +13,6 @@ fn main() {
     }
 }
 
-fn is_a_color_word(attempt: &str) -> bool {
+fn is_a_color_word(attempt: String) -> bool {
     attempt == "green" || attempt == "blue" || attempt == "red"
 }
diff --git a/exercises/strings/strings3.rs b/exercises/strings/strings3.rs
index e2353aec..802e0435 100644
--- a/exercises/strings/strings3.rs
+++ b/exercises/strings/strings3.rs
@@ -5,17 +5,17 @@
 
 fn trim_me(input: &str) -> String {
     // TODO: Remove whitespace from both ends of a string!
-    ???
+    input.to_string().trim().to_string()
 }
 
 fn compose_me(input: &str) -> String {
     // TODO: Add " world!" to the string! There's multiple ways to do this!
-    ???
+    input.to_string() + " world!"
 }
 
 fn replace_me(input: &str) -> String {
     // TODO: Replace "cars" in the string with "balloons"!
-    ???
+    input.to_string().replace("cars", "balloons")
 }
 
 #[cfg(test)]
diff --git a/exercises/strings/strings4.rs b/exercises/strings/strings4.rs
index c410b562..e20dce39 100644
--- a/exercises/strings/strings4.rs
+++ b/exercises/strings/strings4.rs
@@ -16,14 +16,14 @@ fn string(arg: String) {
 }
 
 fn main() {
-    ???("blue");
-    ???("red".to_string());
-    ???(String::from("hi"));
-    ???("rust is fun!".to_owned());
-    ???("nice weather".into());
-    ???(format!("Interpolation {}", "Station"));
-    ???(&String::from("abc")[0..1]);
-    ???("  hello there ".trim());
-    ???("Happy Monday!".to_string().replace("Mon", "Tues"));
-    ???("mY sHiFt KeY iS sTiCkY".to_lowercase());
+    string_slice("blue");
+    string("red".to_string());
+    string(String::from("hi"));
+    string("rust is fun!".to_owned());
+    string_slice("nice weather".into());
+    string(format!("Interpolation {}", "Station"));
+    string_slice(&String::from("abc")[0..1]);
+    string_slice("  hello there ".trim());
+    string("Happy Monday!".to_string().replace("Mon", "Tues"));
+    string("mY sHiFt KeY iS sTiCkY".to_lowercase());
 }
diff --git a/exercises/structs/structs1.rs b/exercises/structs/structs1.rs
index 0d91c469..e550b9af 100644
--- a/exercises/structs/structs1.rs
+++ b/exercises/structs/structs1.rs
@@ -6,9 +6,12 @@
 
 struct ColorClassicStruct {
     // TODO: Something goes here
+    red : u8,
+    green : u8,
+    blue : u8,
 }
 
-struct ColorTupleStruct(/* TODO: Something goes here */);
+struct ColorTupleStruct(u8, u8, u8);
 
 #[derive(Debug)]
 struct UnitLikeStruct;
@@ -20,7 +23,11 @@ mod tests {
     #[test]
     fn classic_c_structs() {
         // TODO: Instantiate a classic c struct!
-        // let green =
+        let green = ColorClassicStruct {
+            red : 0,
+            green : 255,
+            blue : 0
+        };
 
         assert_eq!(green.red, 0);
         assert_eq!(green.green, 255);
@@ -30,7 +37,8 @@ mod tests {
     #[test]
     fn tuple_structs() {
         // TODO: Instantiate a tuple struct!
-        // let green =
+        let green = ColorTupleStruct(0, 255, 0);
+
 
         assert_eq!(green.0, 0);
         assert_eq!(green.1, 255);
@@ -40,7 +48,7 @@ mod tests {
     #[test]
     fn unit_structs() {
         // TODO: Instantiate a unit-like struct!
-        // let unit_like_struct =
+        let unit_like_struct = UnitLikeStruct;
         let message = format!("{:?}s are fun!", unit_like_struct);
 
         assert_eq!(message, "UnitLikeStructs are fun!");
diff --git a/exercises/structs/structs2.rs b/exercises/structs/structs2.rs
index 32e311fa..bdaeae58 100644
--- a/exercises/structs/structs2.rs
+++ b/exercises/structs/structs2.rs
@@ -35,7 +35,12 @@ mod tests {
     fn your_order() {
         let order_template = create_order_template();
         // TODO: Create your own order using the update syntax and template above!
-        // let your_order =
+        let your_order = Order {
+            name : String::from("Hacker in Rust"),
+            count : 1,
+            ..order_template
+        };
+
         assert_eq!(your_order.name, "Hacker in Rust");
         assert_eq!(your_order.year, order_template.year);
         assert_eq!(your_order.made_by_phone, order_template.made_by_phone);
diff --git a/exercises/structs/structs3.rs b/exercises/structs/structs3.rs
index 3536a457..cdb85c1f 100644
--- a/exercises/structs/structs3.rs
+++ b/exercises/structs/structs3.rs
@@ -26,12 +26,14 @@ impl Package {
         }
     }
 
-    fn is_international(&self) -> ??? {
+    fn is_international(&self) -> bool {
         // Something goes here...
+        self.sender_country != self.recipient_country
     }
 
-    fn get_fees(&self, cents_per_gram: i32) -> ??? {
+    fn get_fees(&self, cents_per_gram: i32) -> i32{
         // Something goes here...
+        self.weight_in_grams * cents_per_gram 
     }
 }
 
diff --git a/exercises/tests/tests1.rs b/exercises/tests/tests1.rs
index 8b6ea374..67cfbfba 100644
--- a/exercises/tests/tests1.rs
+++ b/exercises/tests/tests1.rs
@@ -13,6 +13,6 @@
 mod tests {
     #[test]
     fn you_can_assert() {
-        assert!();
+        assert!(true);
     }
 }
diff --git a/exercises/tests/tests2.rs b/exercises/tests/tests2.rs
index a5ac15b1..78d6a6c2 100644
--- a/exercises/tests/tests2.rs
+++ b/exercises/tests/tests2.rs
@@ -9,6 +9,6 @@
 mod tests {
     #[test]
     fn you_can_assert_eq() {
-        assert_eq!();
+        assert_eq!(true, false);
     }
 }
diff --git a/exercises/tests/tests3.rs b/exercises/tests/tests3.rs
index 196a81a0..8ace29d3 100644
--- a/exercises/tests/tests3.rs
+++ b/exercises/tests/tests3.rs
@@ -16,11 +16,11 @@ mod tests {
 
     #[test]
     fn is_true_when_even() {
-        assert!();
+        assert!(is_even(4));
     }
 
     #[test]
     fn is_false_when_odd() {
-        assert!();
+        assert!(!is_even(5));
     }
 }
diff --git a/exercises/variables/variables1.rs b/exercises/variables/variables1.rs
index f4d182ac..c0849eed 100644
--- a/exercises/variables/variables1.rs
+++ b/exercises/variables/variables1.rs
@@ -5,6 +5,6 @@
 // I AM NOT DONE
 
 fn main() {
-    x = 5;
+    let x = 5;
     println!("x has the value {}", x);
 }
diff --git a/exercises/variables/variables2.rs b/exercises/variables/variables2.rs
index 641aeb8e..4b56592b 100644
--- a/exercises/variables/variables2.rs
+++ b/exercises/variables/variables2.rs
@@ -4,7 +4,7 @@
 // I AM NOT DONE
 
 fn main() {
-    let x;
+    let x = 10;
     if x == 10 {
         println!("x is ten!");
     } else {
diff --git a/exercises/variables/variables3.rs b/exercises/variables/variables3.rs
index 819b1bc7..fd01bde6 100644
--- a/exercises/variables/variables3.rs
+++ b/exercises/variables/variables3.rs
@@ -4,6 +4,6 @@
 // I AM NOT DONE
 
 fn main() {
-    let x: i32;
+    let x: i32 = 0;
     println!("Number {}", x);
 }
diff --git a/exercises/variables/variables4.rs b/exercises/variables/variables4.rs
index 54491b0a..ae3d20e9 100644
--- a/exercises/variables/variables4.rs
+++ b/exercises/variables/variables4.rs
@@ -4,7 +4,7 @@
 // I AM NOT DONE
 
 fn main() {
-    let x = 3;
+    let mut x = 3;
     println!("Number {}", x);
     x = 5; // don't change this line
     println!("Number {}", x);
diff --git a/exercises/variables/variables5.rs b/exercises/variables/variables5.rs
index 0e670d2a..65faf126 100644
--- a/exercises/variables/variables5.rs
+++ b/exercises/variables/variables5.rs
@@ -6,6 +6,6 @@
 fn main() {
     let number = "T-H-R-E-E"; // don't change this line
     println!("Spell a Number : {}", number);
-    number = 3; // don't rename this variable
+    let number = 3; // don't rename this variable
     println!("Number plus two is : {}", number + 2);
 }
diff --git a/exercises/variables/variables6.rs b/exercises/variables/variables6.rs
index a8520122..5e1e4321 100644
--- a/exercises/variables/variables6.rs
+++ b/exercises/variables/variables6.rs
@@ -3,7 +3,7 @@
 
 // I AM NOT DONE
 
-const NUMBER = 3;
+const NUMBER:u32 = 3;
 fn main() {
     println!("Number {}", NUMBER);
 }