diff --git a/exercises/13_error_handling/errors1.rs b/exercises/13_error_handling/errors1.rs
index 0ba59a57..4d58fbf9 100644
--- a/exercises/13_error_handling/errors1.rs
+++ b/exercises/13_error_handling/errors1.rs
@@ -9,14 +9,12 @@
 // Execute `rustlings hint errors1` or use the `hint` watch subcommand for a
 // hint.
 
-// 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/13_error_handling/errors2.rs b/exercises/13_error_handling/errors2.rs
index 631fe67f..fbc2ccb6 100644
--- a/exercises/13_error_handling/errors2.rs
+++ b/exercises/13_error_handling/errors2.rs
@@ -19,14 +19,12 @@
 // Execute `rustlings hint errors2` or use the `hint` watch subcommand for a
 // hint.
 
-// I AM NOT DONE
-
 use std::num::ParseIntError;
 
 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>();
+    let qty = item_quantity.parse::<i32>()?;
 
     Ok(qty * cost_per_item + processing_fee)
 }
diff --git a/exercises/13_error_handling/errors3.rs b/exercises/13_error_handling/errors3.rs
index d42d3b17..8222ec43 100644
--- a/exercises/13_error_handling/errors3.rs
+++ b/exercises/13_error_handling/errors3.rs
@@ -7,11 +7,9 @@
 // Execute `rustlings hint errors3` or use the `hint` watch subcommand for a
 // hint.
 
-// I AM NOT DONE
-
 use std::num::ParseIntError;
 
-fn main() {
+fn main() -> Result<(), ParseIntError> {
     let mut tokens = 100;
     let pretend_user_input = "8";
 
@@ -23,6 +21,7 @@ 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/13_error_handling/errors4.rs b/exercises/13_error_handling/errors4.rs
index d6d6fcb6..9b963f30 100644
--- a/exercises/13_error_handling/errors4.rs
+++ b/exercises/13_error_handling/errors4.rs
@@ -3,8 +3,6 @@
 // Execute `rustlings hint errors4` or use the `hint` watch subcommand for a
 // hint.
 
-// I AM NOT DONE
-
 #[derive(PartialEq, Debug)]
 struct PositiveNonzeroInteger(u64);
 
@@ -16,8 +14,13 @@ enum CreationError {
 
 impl PositiveNonzeroInteger {
     fn new(value: i64) -> Result<PositiveNonzeroInteger, CreationError> {
-        // Hmm... Why is this always returning an Ok value?
-        Ok(PositiveNonzeroInteger(value as u64))
+        if value < 0 {
+            Err(CreationError::Negative)
+        } else if value == 0 {
+            Err(CreationError::Zero)
+        } else {
+            Ok(PositiveNonzeroInteger(value as u64))
+        }
     }
 }
 
diff --git a/exercises/13_error_handling/errors5.rs b/exercises/13_error_handling/errors5.rs
index 92461a7e..797a60d4 100644
--- a/exercises/13_error_handling/errors5.rs
+++ b/exercises/13_error_handling/errors5.rs
@@ -22,14 +22,12 @@
 // Execute `rustlings hint errors5` or use the `hint` watch subcommand for a
 // hint.
 
-// I AM NOT DONE
-
 use std::error;
 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/13_error_handling/errors6.rs b/exercises/13_error_handling/errors6.rs
index aaf0948e..562db3e2 100644
--- a/exercises/13_error_handling/errors6.rs
+++ b/exercises/13_error_handling/errors6.rs
@@ -9,8 +9,6 @@
 // Execute `rustlings hint errors6` or use the `hint` watch subcommand for a
 // hint.
 
-// I AM NOT DONE
-
 use std::num::ParseIntError;
 
 // This is a custom error type that we will be using in `parse_pos_nonzero()`.
@@ -26,13 +24,16 @@ 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) -> Result<PositiveNonzeroInteger, ParsePosNonzeroError> {
     // TODO: change this to return an appropriate error instead of panicking
     // when `parse()` returns an error.
-    let x: i64 = s.parse().unwrap();
-    PositiveNonzeroInteger::new(x).map_err(ParsePosNonzeroError::from_creation)
+    let poseNonzero = s.parse().map_err(ParsePosNonzeroError::from_parseint)?;
+    Ok(PositiveNonzeroInteger::new(poseNonzero).map_err(ParsePosNonzeroError::from_creation)?)
 }
 
 // Don't change anything below this line.