Question

what is the net force of the box and which direction will it move (50 N left, 50N left and 100 N right)​

Answer 1

the net force is 0 and it will not move

Answer 2

The net force on the box is zero.

-- If it was already moving when the forces began, it continues moving in a straight line with constant speed.

-- If it was NOT already moving when the forces began, then it won't start moving, because the forces are 'balanced', and their effect on the box is the same as if there were no forces there at all.