Question

a body of weight 5 n is kept on a smooth horizontal table . find the force exerted by the table on the body .

Answer 1

The force exerted by the body on the table is 5 Newton.
It is because the force applied by the book on the table is 5N vertically downwards.
The weight of the book thus balances the force applied in the opposite direction.

Answer 2

smooth horizontal table means there is no frictional force on the surface.
the body exerts a force of 5Newtons on the surface of table at the point of contact, in a downward direction. This force is equal to its weight.
as per the newtons  law,  the table exerts a force 5 N in the opposite direction on the body at the point of contact or surface of contact.  (equal & opp reaction)