Merge pull request #29 from Meg528/patch-21

Update group.mdx

Author: dfreniche

docs/70-grouping/group.mdx

@@ -11,7 +11,7 @@ db.books.aggregate([
 ])
 ```
 
-Here, we group by book's `year` (the _id of the grouping), and then we create a new field called `totalPages` that's the sum of all pages.
+Here, we group by the book's `year` (the _id of the grouping), and then we create a new field called `totalPages` that's the sum of all pages.
 
 👐 Can you get the results ordered ascending by year?
 
@@ -49,7 +49,7 @@ db.books.aggregate([
 </div>
 </details>
 
-👐 Which year had the most printed out pages?
+👐 Which year had the most printed-out pages?
 
 <details>
 <summary>Answer</summary>
@@ -66,4 +66,4 @@ db.books.aggregate([
 ])
 ```
 </div>
-</details>
+</details>