First, let’s figure out how much of his money he spent on the total amount of books.
We’ll take his staring amount ($331) and subtract it by how much money he had left over ($16)
$331 - $16 = $315
So now we know that he spent $315 for ALL the books.
Now, we divide $315 by how many books he purchased (9) to find out how much he paid for EACH book
$315 ÷ 9 = $35
Therefore, EACH book costs $35
Hope this helps you
- AaronWiseIsBae