Correct answer is (4):

Hakkem made purchase of x dollars which is first deducted by $15 which is x-15 and then that price is lower by 20% which means that Hakkem will pay only 80% of (x-15) dollars, so we have equation:

(x-15)*0.80 = 0.80x - 12

Your question is not clear. To find what is the value of x you must know what is the value of Hakeem's purchase.

Let's say he made a total purchase of y dollars.

So we have.

0.80x-12=y

In terms of x solution is:

x=(12+y)/0.80