What is the rate of 2 cars traveling in the same direction i

What is the rate of 2 cars traveling in the same direction if they leave the same place at the same time. The rate of one car is twice as fast as the other and after 4 hours the faster car is 80 miles ahead of the slower car.

Solution

rt=d
rate*time =distance
x=2y
2x=4y
after 4 hours y goes 4y
4x=80+(4y)
4x=80+2x
2x=80
x=40 mph
x=2y
40=2y
y=20 mph
check
4*40=160
4*20=80
160-80=80