With the wind, a jet can fly 2500 km in 2 hours 30 minutes. against the wind, it can fly only 2000 km in the same amount of time. find the rate of the jet in still air and the rate of the wind.

With the wind, a jet can fly 2500km in 2 hours 30 min.
With wind DATA: 
distance = 2500 km ; time = 2.5 hrs ; rate = 2500/2.5 = 100 km/h

Against the wind, it can fly only 2000km in the same time.
Against wind DATA:
distance = 2000 km ; time = 2.5 hrs ; rate = 2000/2.5 = 800 kmh

Find the rate of the jet in still air and the rate of the wind.

p + w = 100
p - w = 80

2p = 180
p = 90 kmh (plane speed in still air)

Since p+w = 100, w = 10 kmh (wind speed)

The answer is all about the number 4