9:30-9:00= 30 minutes 30 mins= half hour so since you said 10 miles per hr it would be easier if we make it like 5 miles per 30 minutes. Because to solve for distance we need to multiply speed x time so speed was 10miles per hr/ 5 miles per .5hrs( 30 mins) and the time was 30 minutes which is 1/2 or .5hr. 10 x .5 =5 miles per hr :) question (sorry for making it sound confusing)