Grammar fixups

Author: ehershey

book/src/08_futures/03_runtime.md

@@ -41,7 +41,7 @@ across threads.
 ## Implications
 
 `tokio::spawn` is flavor-agnostic: it'll work no matter if you're running on the multithreaded
-or current-thread runtime. The downside is that the signature assume the worst case
+or current-thread runtime. The downside is that the signature assumes the worst case
 (i.e. multithreaded) and is constrained accordingly:
 
 ```rust

exercises/08_futures/03_runtime/src/lib.rs

@@ -1,5 +1,5 @@
 // TODO: Implement the `fixed_reply` function. It should accept two `TcpListener` instances,
-//  accept connections on both of them concurrently, and always reply clients by sending
+//  accept connections on both of them concurrently, and always reply to clients by sending
 //  the `Display` representation of the `reply` argument as a response.
 use std::fmt::Display;
 use tokio::io::AsyncWriteExt;