Carla rode her bike 30 miles in 2 1/2 parks
To find out Carla's average speed per hour, we need to convert the time taken to hours.
2 1/2 hours is equal to 2 + 1/2 = 2.5 hours.
Now, to find the average speed, we divide the total distance traveled by the total time taken:
Average speed = Total distance / Total time
Average speed = 30 miles / 2.5 hours
Average speed = 12 miles per hour.