Explanation:
Average speed is the total distance traveled divided by the total time elapsed. In this case, the total distance traveled is 0 miles because she ended up at the same place where she started. The total time elapsed is the time it took her to ride the roller coaster. Since we don't know how long that took, we can't calculate the average speed.
Average velocity is the displacement (change in position) divided by the time elapsed. In this case, the displacement is also 0 miles because she ended up at the same place where she started. Therefore, the average velocity is also 0 mph.