When two forces act on an object in opposite directions, the net force can be calculated by subtracting the two forces.
Explanation:
For example: If you keep a bottle on the table, the downward force subtracted from the upward force will be equal to the net force.
For example: In the tug of war when two forces are of different units the force with the greater strength will have an advantage, like if the team on the right is stronger than that of left than the rope will move towards the right.