What is the rate of the plane in still air and what is the rate of the wind?

Question

Flying against the wind, an airplane travels 3960 km in 6 hours. Flying with the wind, the same plane travels 7000 km in 7 hours. What is the rate of the plane in still air and what is the rate of the wind? 

Answer 1

3960 = (R-S)*6 = 6R - 6S

7000 = (R+S)*7 = 7R + 7S

10960 = 13R + S

S = 10960 - 13R

3960 = 6R - 6( 10960 - 13R)

3960 = 6R - 65760 + 78R

69720 = 84R

R=830

S = 10960 - 13*830 = 170

The speeds of the plane and wind are

840 kmh and 170 kmh.

Pretty fast plane.... pretty fast wind