Astriped billiard ball rolls and strikes a motionless solid billiard ball. the solid ball then begins to roll. which best describes the change in the magnitudes of momentum for the balls?

This situation can be best explained by the conservation of momentum. The momentum of the rolling ball is passed on to the motionless solid ball. After collision, the then rolling ball slows to a stop, while the then motionless solid ball moves with the same magnitude of momentum as that of the striped billiard ball.