Question 449482
plane speed = x mph
wind speed = y mph

with wind speed = (x+y)
against wind speed = (x-y)

3600/(x+y)=4
4x+4y=3600
/4
x+y=900....................1
 3600/(x-y)=5
3600=5x-5y
x-y=720....................2

Add (1) +(2)
2x=1620
x=810 mph speed of plane
900-810= 90 mph speed of wind