When going more than 38 miles per hour, the gas mileage of a certain car fits the model y=43.81-0.395x where x is the speed of the car in miles per hour and y is the miles per gallon of gasoline. Based on this model, at what speed will the car average 15 miles per gallon? (Round to nearest whole number.)

Question

When going more than 38 miles per hour, the gas mileage of a certain car fits the model y=43.81-0.395x where x is the speed of the car in miles per hour and y is the miles per gallon of gasoline. Based on this model, at what speed will the car average 15 miles per gallon?  (Round to nearest whole number.)

anonymous · Answer

plug in 15 for the miles per gallon or 'y'

15=43.81-0.395x

now solve for x

anonymous · Answer

so what is it?