A car gets 21 mi/gal in city driving and 28 mi/gal highway driving. If 18 gal of gas are used in traveling 448 mi, how many miles were driven in the city, how many driven on the highway (assuming that only the given rates of usage were actually used)?

Answer 1

A car gets 21 mi/gal in city driving and 28 mi/gal highway driving. If 18 gal of gas are used in traveling 448 mi, how many miles were driven in the city, how many driven on the highway (assuming that only the given rates of usage were actually used)?

H = highway gallons and C = city gallons.
Then,
H + C = 18 and

21C + 28H = 448.

I suspect you can take it from here.