Question

Flying against the wind, an airplane travels 5600 km in 8 hours. Flying with the wind, the same plane travels 9900 km in 9 hours. What is the rate of the plane in still air and what is the rate of the wind?

Answer 1

guess we have to use "distance equals rate times time"
and we need a variable for the rate
what do you pick?

Answer 2

Against the wind
distance = (air speed -wind speed) * time
5,600 = (air speed - wind speed) * 8
let x = air speed and y = wind speed
5,600 = (air speed - wind speed) * 8
5,600 = (X - Y) * 8

With the wind
distance = (air speed +wind speed) * time
9,900 = (X+Y) * 9

So, now we have 2 equations
5,600 = (8X - 8Y)
9,900 = (9X + 9Y)

Solve the equations and you'll have your answer