Hi
Let x represent the amount of time before the plane overtakes the car
D = r*t, distance traveled the same for both car and plane
Question States***
80mph(x + 1hr) = 400mph*x
solving for x
80 = 320x
x = 1/4hr, the amount of time before the plane overtakes the car
CHECKING our Answer
80*5/4 = 1/4*400 = 100mi (the distance traveled by both when plane passes)