What is the area of this quadrilateral

What's the difference between: x≥0 and nonnegative integer. ?

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.

4+(2+x) can you me solve this problem