Determine whether the system of linear equations has one and only one solution, infinitely many solutions, or no solution. find all solutions whenever they exist.
x + 3y = 9
3x –y = 7

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.