Answer:
The expression is;
Number of books = length of box/thickness of book
= 81/2/9 = 81 books
Explanation:
Here, we want to determine the number of books that will fit into a box given the length of the book and the box.
The expression that can be used to get the number of books will be;
Number of books = length of box/thickness of book
= 18 divided by 2/9
= 18 * 9/2 = 81 books