System or no system required? This is entire question

Question

You drove 280 miles. The cost of gasoline was $4.15 per gallon. If you get 24 mi/gal on the highway and 16 mi/gal in the city:

a) How much did you spend for fuel on highway driving?

b) How much for city driving?

Answer 1

Total distance is 280 miles (which could be city, highway, or combination of the two)

City distance is 280 total miles - highway miles

Highway distance is 280 total miles - city miles

Cost will be the distance divided by rate times the cost per gallon, so-

a) Highway cost will be 280 - city miles (if any)/24 times 4.15

b) City cost will be 280 - highway miles (if any)/16 times 4.15

Answer 2

a) (280 / 16)($4.15) = ?

b) (280 / 24)($4.15) = ?