Who is asking: Student
It takes 6 hours for a plane to travel 720 km with a tail wind and 8 hours to make the return trip with a head wind. Find the air speed of the plane and the speed of the wind current.
There are two speeds here, the wind speed, and the speed that the plane would fly if there was no wind, called the air speed of the plane. Give variable names to these two quantities. Let W be the wind speed in kilometers per hour and let P be the air speed of the plane in kilometers per hour. You can add speeds so, if the plane flies in the same direction as the wind then the plane moves at P + W kilometers per hour and if the plane flies against the wind then the plane moves at P - W kilometers per hour. Hence for your problem you have
P - W = 720/8 = 90 km/hr
Solve for P and W.