Question

a man with a mass of 90,6 kg walks to the back of a train at a velocity of 1m/s while the train moves at a constant velocity of 36km/h in a easterly direction. what is the weight of the man

Answer 1

1. There is no vertical motion, so no vertical acceleration.
2. The velocities are constant anyway, again no acceleration.
So
weight = m g = about 90.6 * 9.81 Newtons

Someone is trying to confuse you.

Answer 2

A man with a mass of 95kg walks to the back of train at a velocity of 1.3m/s while the train moves at a constant velocity of 45km/h in an easterly direction