A soccer camp charges athletes an initial fee, then a weekly fee. The total amount of money paid by two athletes are given by the functions f(x) and g(x) where x is the number weeks they have attended the camp. The graphs of f and g are parallel lines (shown below). Did the two athletes pay the same initial fee, or the same weekly fee?

Because these two lines don’t have the same y-intercept, it means that they didn’t pay the same initial fee. Since they are parallel, it means that they paid the same weekly fee.