The braking distance, D, of a car is directly proportional to the square of its speed, v. When d=5, v=10 Find d when v=70

Martha is training for a duathlon, which includes biking and running. she knows that yesterday she covered a total distance of over 55.5 miles in more than than 4.5 hours of training. martha runs at a speed of 6 mph and bikes at a rate of 15.5 mph.