When a plane flies with the wind, it can travel 1980 miles in 4.5 hours. when the plane flies in the opposite direction, against the wind, it takes 5.5 hours to fly the same distance. find the velocity of the plane in still air and the average velocity of the wind.

Velocity with wind = 1,980 / 4.5 = 440 mph
Velocity against wind =1,980 / 5.5 = 360 mph
Plane in still air - wind speed = 360
Plane in still air + wind speed =440
Adding both equations:
2*Plane in still air = 800
Plane in still air = 400 mph
Plane in still air + wind speed =440
Therefore, wind speed = 40 mph