The distance fomrula is: distance = rate x time
For example, if you were travelling at 60 miles per hour and you have driven for 3 hours, the distance that you went was 180 miles.
distance = (60 mi / hr) x (3 hrs) <--- multiply to get the answer
If the distance was 100 miles and it took 2 hours, your rate was 50 miles per hour.
100 miles = rate x (2 hrs) <--- divide both sides by 2 hrs to get the answer
If the distance was 200 miles and the rate was 50 miles per hour, you time was 4 hours.
200 miles = (50 mi / hr) x time <--- divide both sides by 50 miles per hour to get the answer