Charlie paid $660 for six shirts and four belts. One shirt costs three times as much as one belt. If Sam bought five such shirts and two such belts, how much would he have to pay?

This is a system of equations. Let s be the price of a shirt and b be the price of a belt. Turn words into math. Here is one of the equations:

s = 3b.

Find the other and solve. I'd recommend using substiution.