Fix typo:a X or and O:an X or an O

src/content/learn/tutorial-tic-tac-toe.md

@@ -1406,7 +1406,7 @@ But wait, there's a problem. Try clicking on the same square multiple times:
 
 The `X` is overwritten by an `O`! While this would add a very interesting twist to the game, we're going to stick to the original rules for now.
 
-When you mark a square with a `X` or an `O` you aren't first checking to see if the square already has a `X` or `O` value. You can fix this by *returning early*. You'll check to see if the square already has a `X` or an `O`. If the square is already filled, you will `return` in the `handleClick` function early--before it tries to update the board state.
+When you mark a square with an `X` or an `O` you aren't first checking to see if the square already has a `X` or `O` value. You can fix this by *returning early*. You'll check to see if the square already has a `X` or an `O`. If the square is already filled, you will `return` in the `handleClick` function early--before it tries to update the board state.
 
 ```js {2,3,4}
 function handleClick(i) {
@@ -1556,7 +1556,7 @@ It does not matter whether you define `calculateWinner` before or after the `Boa
 
 </Note>
 
-You will call `calculateWinner(squares)` in the `Board` component's `handleClick` function to check if a player has won. You can perform this check at the same time you check if a user has clicked a square that already has a `X` or and `O`. We'd like to return early in both cases:
+You will call `calculateWinner(squares)` in the `Board` component's `handleClick` function to check if a player has won. You can perform this check at the same time you check if a user has clicked a square that already has an `X` or an `O`. We'd like to return early in both cases:
 
 ```js {2}
 function handleClick(i) {