a man of weight W is standing on a lift which is moving upward with an acceleration A. What is the apparent weight of man?

Let, ‘m’ be  the mass of the man, ‘g’ be the acceleration due to gravity, ‘a’ is the acceleration of the lift upwards.

Forces on the floor by the man are:

Gravitational force downward = mg

The reaction on the floor due to the upward acceleration of the lift = ma

So, the net force on the floor by the man = mg + ma = m(g + a)

This force m(g + a) is the apparent weight of the man.