I reccomend the search bar up at the top ("What is your question") before you ask questions, to make sure they're not already answered.
There is a formula d = rt, distance = rate*time. So
r = d/t.
r = 7mi/55min = 0.127mi/min
Or another way to see this:
[tex] \frac{7 miles}{55min} \frac{/55}{/55} = 0.127 mi/min[/tex]