Answer:
5 miles per hour.
Explanation:
To solve this problem we first have to calulate the rate at which Justin ran the first day, that is done by dividing the distance by the time:
Rate=distance/time
Rate= 15/2.5
Rate= 6 miles per hour
Since he ran at 6 miles per hour and the next day he ran 1 mile per hour slower he would have run at a 5 mph rate the next day.