Question 959269
A jet plane flying with the wind flew 2200 km in 4 hours. Flying against the wind, the plane could fly only 1820 km in the same amount of time. Find:
a) The rate of the plane in calm air and,
b) The rate of the wind 
travel time=distance/rate
***
let x= rate of the plane in calm air
let c= rate of the wind 
(x+c)=rate of plane with wind
(x-c)=rate of plane against wind
..

4(x+c)=2200
4(x-c)=1820
..
4x+4c=2200
4x-4c=1820
add
8x=4020
x=502.5
..
subtract:
8c=380
c=47.5
rate of the plane in calm air=505.2 km/h
rate of the wind =47.5 km/h