speed and current question

Question

Flying against the wind, an airplane travels 8640 kilometers in 9 hours. Flying with the wind the same plane travels 11,040 kilometers in 8 hours what is the rate of the plane in still air and what is the rate of the wind

Answer 1

p-w=8640/9= 96

p+w = 11040/8 = 1380

add

2p= 1476

p= 738 mph = plane speed still air

w = wind speed = -642 mph