The given formula above, y = -x, is a sample of a function. A function is an equation that would give only one value of y for every value of x. This is the same as saying that exactly one output is set by each input. If we take x = -1, the value of y is 1 and nothing else.
You have to find the unit rate of the average cost per visit so I think you have to divide 269.50 by 14 which equals 19.25 and I think that is your answer