The cost in dollars is given as 50 + 0.50x, so ... f(x) = 0.50x +50
B) You want to find x for f(x) = 100. Substitute the given numbers and solve for x. 100 = 0.50x +50 50 = 0.50x 50/0.50 = x 100 = x You drove 100 miles during the week if the cost was $100.
