Question 325523
Let speed of plane be xmph
speed of wind be y mph
..
with wind  speed = x+y
distance = 1200
Time = 1200/x+y = 2.5
1200=2.5x+2.5y................1
..
Against wind speed = x-y
disatnce = 1200
time = 1200/x-y=3
1200= 3x-3y...............2
..
multiply equation 1 by 3 and equation 2 by 2.5
3600=7.5x+7.5y
3000=7.5x-7.5y
By adding the two equations
6600=15x
x=440 mph speed of plane
plug the value  of x in the equation 2
1200= 1320-3y
3y=120
y= 40 mph speed of wind