wind speed = x
planes speed with wind: 480-x
planes speed against wind: 440+x
set them to equal and solve for x ( wind speed)
480-x = 440 +x
add x to each side:
480 = 440 +2x ( x+x=2x)
480 = 440 +2x
subtract 440 from each side:
40 = 2x
divide both sides by 2
x = 40/2
x = 20
wind speed = 20 miles per hour
speed of plane in still air = 480-20 = 460 miles per hour
