Answer;
Speed of the airplane in still air = 50 mph
Speed of the wind = 10 mph
Solution;
Against wind:
Distance = 120 miles ; time = 2 hrs. ; rate = 120/3 = 40 mph
With wind :
Distance = 120 miles ; time = 2 hrs ; rate = 120/2 = 60 mph
Equations:
p + w = 60 (with wind)
p - w = 40 (against the wind)
2p = 100
p = 50 mph (speed of the plane in still air)
Since p+w = 60, then; w = 60-50 = 10 mph (speed of the wind)