Make n (normal) the speed of the plane without wind resistance

make w the wind speed

With the wind

distance = 960 miles ; time = 4 hrs ; speed = 960/4= 240 mph

Against the wind

distance = 960 miles ; time = 6 hrs ; speed = 960/6 = 160 mph

Use these equations:

N - w = 160 mph (miles per hour)

n + w = 240 mph

n - w + n + w = 160 +240 mph

2n = 400 mph

n = 200 mph (speed of the plane in calm air)

200 + w = 240

w = 40 mph (wind speed)

make w the wind speed

With the wind

distance = 960 miles ; time = 4 hrs ; speed = 960/4= 240 mph

Against the wind

distance = 960 miles ; time = 6 hrs ; speed = 960/6 = 160 mph

Use these equations:

N - w = 160 mph (miles per hour)

n + w = 240 mph

n - w + n + w = 160 +240 mph

2n = 400 mph

n = 200 mph (speed of the plane in calm air)

200 + w = 240

w = 40 mph (wind speed)