Final answer:
When a student jumps off a skateboard to the east, the skateboard will move towards the west due to the law of action-reaction.
Step-by-step explanation:
According to the law of action-reaction, when a student jumps off a skateboard to the east, the skateboard will move in the opposite direction, which is towards the west. This principle is also known as Newton's Third Law, which states that for every action, there is an equal and opposite reaction. The force exerted by the student on the skateboard as he jumps off pushes the skateboard in the opposite direction of the student's jump. This is similar to how when a person jumps from a boat to a dock, the boat moves backward. The skateboard's motion is the reaction to the student's action.