Step-by-step explanation:
The direction of the force towards the right is positive while those towards the left is negative:
If a team of astronauts pulls a satellite to the right with a force of 1,200 N, then the force is+1200N
If another team pulls the satellite to the left with a force of 1,500 N, then the force is -1500N
Net force = -1500+1200
Net force = -300N
The net force is 300N towards the left (it was to the left due to the negative value of the force)