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.
In terms of x solution is: