Question 311992
let speed of plane in still air be x
let speed of wind be y
..
speed with wind = x+y
2(x+y)=600
..
speed against wind = x-y
2.5(x-y)=600
multiply by 10
25x-25y= 6000( multiply by 2)
2x+2y=600 ( multiply by 25)
ADD
..
50x-50y+50x+50y= 12000 +15000
100x=27000
x=270 mph speed in still air