What is the inverse operation for " add 15.3"

Pyotr tchaikovsky sporting goods operates on a 45% overhead based on the selling price, which results in an overhead of $65.34 on the newest version of an air hockey game set. if the air hockey game set costs pyotr tchaikovsky sports $49.32, find the selling price, the markup, and the net profit.

Which one is the correct answer, and why?

What is the approximate value of  x  in the equation below.–3.396–0.7080.3040.955