Entire distance = 1,320
Entire time = 5 hours
bus avg = 40 km/h
plane avg = 600 km/h
Working this by trial and error
1 hour bus 4 hour plane = 40 + 2,400 = 2,800 distance (too high)
2 hour bus 3 hour plane = 80 + 1,800 = 1,880 distance (too high)
3 hour bus 2 hour plane = 120 + 1,200 = 1,320 distance (Correct!!)
So, they traveled 3 hours by bus and 2 hours by plane
(yes, you had the right answer).
