Question 36887
Flying against the jetstream, a jet travels 6390 km in 9 hours. Flying with the jetstream, the same jet travels 5150 km in 5 hours. What is the speed of the jet in still air, and what is the speed of the jetstream? 

Against the wind Data:
distance=6390km; time=9 hrs; rate=710kph
With the wind Data:
distance=5150km; time=5hrs; rate=1030kph
EQUATIONS:
airspeed+jetstream=1030
airspeed-jetstream=710
Subtract these equations to get:
2jetstream=320kph
jetstream=160mph

Cheers,
Stan H.