if a 200n action force is exerted to the left, what is the reaction force?

Question

 I am studying for my final and am struggling with finding out the formula and/or answer to this question. I would appreciate it if someone could help out, thank you.

Answer 1

This is Newton's Third Law of motion.  Every action has an opposite and equal reaction.

 

Reaction force is 200n exerted to the right.