A passenger plane ad a jet leave at the same time from the s

A passenger plane ad a jet leave at the same time from the same airport, traveling in opposite directions. The jet travels at twice the speed of the passenger plane. They are 2400 miles apart in 4 hours. Find the speed of the passenger plane and the jet.

rt=D
(x+2x)4=2400
12x=2400
x=200 mph passenger plane
2x=400 mph jet