Grammar typo (#7)

Fix a nano-typo in 04_panics.md

book/src/02_basic_calculator/04_panics.md

@@ -38,7 +38,7 @@ fn main() {
 }
 ```
 
-There are other mechanism to work with recoverable errors in Rust, which [we'll cover later](../05_ticket_v2/06_fallibility).
+There are other mechanisms to work with recoverable errors in Rust, which [we'll cover later](../05_ticket_v2/06_fallibility).
 For the time being we'll stick with panics as a brutal but simple stopgap solution.
 
 ## References

book/src/02_basic_calculator/10_as_casting.md

@@ -46,7 +46,7 @@ To understand what happens, let's start by looking at how `256u16` is
 represented in memory, as a sequence of bits:
 
 ```text
- 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0
+ 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0
 |               |               |
 +---------------+---------------+
   First 8 bits    Last 8 bits

book/src/07_threads/14_sync.md

@@ -14,7 +14,7 @@ For example: `MutexGuard` is not `Send`, but it is `Sync`.
 
 It isn't `Send` because the lock must be released on the same thread that acquired it, therefore we don't 
 want `MutexGuard` to be dropped on a different thread.  
-But it is `Sync`, because that has no impact on where the lock is released.
+But it is `Sync`, because giving a `&MutexGuard` to another thread has no impact on where the lock is released.
 
 ## `Send` doesn't imply `Sync`
 

exercises/01_intro/00_welcome/src/lib.rs

@@ -5,7 +5,7 @@
 // explanations.
 // There are various ways to write comments in Rust, each with its own purpose.
 // For now we'll stick to the most common one: the line comment.
-// Everything from `//` to the end of the line is a considered comment.
+// Everything from `//` to the end of the line is considered a comment.
 
 // Exercises will include `TODO`, `todo!()` or `__` markers to draw your attention to the lines
 // where you need to write code.

exercises/03_ticket_v1/02_validation/src/lib.rs

@@ -34,7 +34,7 @@ mod tests {
     #[test]
     #[should_panic(expected = "Title cannot be empty")]
     fn title_cannot_be_empty() {
-        Ticket::new("".into(), valid_title(), "To-Do".into());
+        Ticket::new("".into(), valid_description(), "To-Do".into());
     }
 
     #[test]