Answer: So, if the forces are in the same direction, it'll be 50N+30N= 80N!
If the forces are in opprsite direction it'll be 50N-30N= 20N (or visa-versa)
Explanation: This is because if the forces are in the same direction, like 2 people are pushing a body with 0 mass (I know, weird but imagine it) and both the people are applying the force in the same direction, let's say East, so the total fore exerted on the body will add up to become 50N+30N=80N.
And if the forces are phusing the body in oposite direction, then, let's say the bigger guy is pushing on the West Direction with 50N of force and the weaker guy is pushing on the opposite direction with 30N of force, so this time their forces cancel out and it becomes 50N-30N= 20N (or 30N-50N= -20N).