Question 874262
When the second plane catches up the distance traveled by both is the same

first plane speed = 240 km/h
time = x

distance = 240(x)

Second plane speed = 600 km/h
time = (x-3)

distance = 600(x-3)

240x=600(x-3)

240x=600x-1800

360x=1800
x=5 hours

second plane starts 3 hours later
5-3=2 hours