We know that she runs 8 miles in 3 hours and we have to find how much time it takes to run 3 miles.
Let time be x and now lets put in the numeric form.

=

now cross multiplying each other so we get
8 * x = 3 * 3
8x = 9 { dividing both sides by 8 }
x = 9/8orx = 1.125 hrs.