$18. Multiply 30 by 0.4 and subtract that value from 30 to get the price after the percentage taken away.
gas mileage = k*s, where k is a constant of proportionality and s is the speed. Unfortunately, this does not take into account the fact that the engine consumes fuel even when the car is not moving.
Here it makes most sense to regard {0, S} as the domain for this function. Here, S would represent the car's top speed.
Answer: -5x+-10 using the distributive property
