Question 667753
velocity of wind = x mi/h
with wind speed  of plane = 120 +x mi/h

D1= (120+x)*4

against wind speed = 120-x mi/h
D2= (120-x)*4

D2= 3/5 D1

3/5(120+x)*4 = (120-x)*4

3(120+x)=5(120-x)
360+3x=600-5x
8x= 240
x=30

wind speed = 30 mi/h