Answer:
I would have to say A) 32 + 45 + 39: 3
Explanation:
This is because when finding the average of literally anything, you want to add up all the numbers, and then divide the sum of it by the numbers you added up.
for instance: 32 + 45 + 39 = 116. now, we need to divide by 3 because we added 3 numbers up.
116 divided by 3 = x
x is our average cost per books.
hope this helped, gl on your test!! :')