Newton's third law of motion states that there is always an equal and opposite reaction to every action. This means that the amount of force exerted upon an object is equal to the amount of force the object exerts but in an opposite direction.
This is the case in this scenario where a student sits at rest in a chair. The student is supplying the action force being exerted on the chair. According to the third law of Newton, the chair will exert the same size of force back in the student but in an opposite direction.
Hence, the force the chair exerts on the students compare with that of the student in the sense that they are the same magnitude (size) but the opposite directions.
