A sound system normally priced at $530 is on sale for 25% off. Find the discount and the sales price. Would I write the equation (0.25)(530)=13.25 and 530-13.25=516.75?
Your $516.75 and his $387.50 are WRONG.
Correct amount: $397.50.
Surely I don't need to show/tell you how to obtain that correct answer, do I?