Answer:
Velocity of the passenger = 78.8[km/h]
Explanation:
In order to solve this problem, we must observe the train from a distant point of the train. In this way we can observe that the train moves at 80[km/h] relative to the ground.
In such a way that the passenger moves in a direction contrary to the movement of the train.
The Observer located outside the train will see how the passenger moves away at 78.8 [km / h] and not at 80[km/h] which is the speed of the train.