To find the original price of each apple, after considering the discount for buying 4 or more, you first need to determine the effective price per apple without the discount. Since Eve bought 12 apples for $15, the operation that should be done first in this context is dividing the total cost by the number of apples to find the effective price per apple, which is:
divide 15 by 12
So, the correct response is: divide 15 by 12.