Question

Two cars leave the origin; one goes north at 45 mph and the other goes south at 30 mph. after how many hours will they be 400 miles apart?

Answer 1

400 = 45x + 30x
400 = 75x
5.333 = x

Lets test

45mph for 5.333 hours = 240 miles
30mph for 5.333 hours = 160 miles
240 + 160 = 400 miles apart.