An airplane, a car and a man all move in the same direction, but with different velocities. How will their movements be recorded by different observers?

The relative velocity of two bodies is the velocity of one of them, measured in a frame of reference attached to the other body. If the first body`s velocity is V1, and the velocity of the frame of reference with respect to the earth is V0, then the relative velocity equals to  V1- V0.

Initial Values of Parameters
Velocity of men (V1 ) 5 km/h
Velocity of car (V2 ) 20 km/h
Velocity of airplane (V3 ) 80 km/h