Two cars leave San Francisco at the same time traveling in opposite directions. One travels at an
average speed of 74 mph and the other at 78 mph. In how many hours will they be 304 miles apart?
Let x = time of travel for the first car and y = time of travel for the second car.
Then the system that
models the problem is {74x + 78y=304}
Solve the system by using the method of addition.