Is there 4 arrows? Cause from the question, it looks like there is four arrows, anyways, net force is defined as the sum of the forces. We can look at this from a component view point.
First lets take a look at vertical forces. There is a force pointing downwards by -4N, there is another force pointing upwards which is +4N. The sum of these forces is 0, so the net force is 0. This tells us that there is no force acting on the box in the vertical direction.
Next let's examine the horizontal forces. There is a force pointing back -2N and another force pointing in the positive direction 5N. The sum of these forces is 3N, meaning there is a force of 3N being applied in the positive x-direction, or to the right.
So the total net force is 3N to the right.