Average Speed = Distance (miles) / Time (hours)
Distance = 25 miles
Time = 2 hours 15 minutes
15 minutes to hours = 15 minutes / 60 minutes = 15/60 = 0.25 hour
2 hours 15 minutes = 2 hours + 0.25 hours = 2.25 hours
Speed = 25 miles / 2.25 hours = 11.111 miles per hour
Speed = 11.111 miles per hour
Hope this helps.