Answer:
43 minutes.
Step-by-step explanation:
f(x) is the time in minutes that a customer will wait when x cars are ahead of the customer.
If a customer is 5th in the line, it means there are 4 cars ahead of that customer.
So, the time that customer waits is equal to f(4)
f(4) = 7 × 4 + 15
f(4) = 28 + 15
f(4) = 43 minutes