Question 347767
let speed of plane be xmph
speed of wind = y mph
..
time = distance /speed
speed upwind = x-y
speed downwind = x+y
time = 2160/x+y=3
x+y = 2160/3
x+y=720........................1
upwind 
time = 2160/x-y = 4
2160/4 = x-y
340 = x-y......................2
add equation 1 & 2
2x= 1060
x= 530 mph
.....
x+y=720
530+y=720
y=720-530
y= 90 mph