A plane flies 720 miles with the wind in 3 hours. The return trip against the wind takes 4 hours. What is the speed of the wind and the speed of the plane in still air?

Let p and w represent the speed of the plane and the speed of the wind, respectively.

... speed = distance/time

... p + w = 720/3 = 240

... p - w = 720/4 = 180

Add the two equations to eliminate w.

... 2p = 420

... p = 210

... w = p - 180 = 30

The speed of the wind is 30 mph.

The speed of the plane in still air is 210 mph.