Okay, so we're starting with d = rt.
"Distance equals rate times time."
If you divide both sides by t, you would get r = d/t.
So, your answer is A.
Another explanation: let's say you've traveled 120 miles in 2 hours. How fast were you going? To solve that, you would divide your distance (120) by your time (2) to get 60 mph. So, rate = distance/time.
Hope this helps.
