Answer:
$35
Explanation:
1) Calculate how much was spent
If Benny started with 332 dollars and was left with 17 dollars to find how much he spent we just need to subtract them
2) Find out how much one cost
If 315 dollars was spent on 9 books to find out how much just 1 book cost we need to divide the values
Meaning that one book cost $35
Hope this helps, have a great day!