Answer:
Net force acting on the box,

Step-by-step explanation:
It is given that,
Force with which the box is pushed, F = 20 N
Force acting due to sliding friction, f = 7 N
Sliding friction is a type of resistive force. It always opposes the motion of an object. Here, the force of 7 N will act in the opposite direction of motion. As a result, the net force acting on the box is given by :



So, the net force acting on the box is 13 N. Hence, this is the required solution.