Luke is keeping track of the total number of hours he exercises. He started the summer having already put in 15 hours, and he then exercises 7 hours each week. The function to keep track of his exercise is f(x) = 7x + 15. What do the f(x) and x represent in Luke's situation? f(x) represents the total number of hours; x represents the number of weeks he exercises this summer f(x) represents the total number of weeks that he has exercised; x represents the number of hours f(x) represents the number of hours he exercises per day; x represents the number of weeks f(x) represents the total number of hours that Luke has exercised; x represents the number of weeks he exercises per day