Final answer:
When you push on a wall with a force of 20N east, the wall exerts a reaction force of the same magnitude, 20N, but in the opposite direction, which is west.
Step-by-step explanation:
The question is about Newton's third law of motion which states that for every action, there is an equal and opposite reaction. When you push east on a wall with a force of 20N, the wall pushes back with an equal force in the opposite direction. According to Newton's third law, the magnitude of the reaction force is equal to the magnitude of the force exerted on the wall, which is 20N, and the direction of the reaction force is exactly opposite to the direction of the applied force, which is west.
Therefore, the correct answer to the question is:
Magnitude = 20N, Direction = West.