The conversion factor for mph to ft/s is 22/15, so 35mph=35×22/15=154/3 ft/s.
5mph=5×22/15=22/3 ft/sec. So the speed is lowered to 14.72-7.33=7.387 approx.
Therefore the original speed is 14.72/7.387=1.993 times the new speed, or 1.99 rounded to 2 dec places.
The conversion factor was calculated from knowing that there are 5280 ft in a mile and 3600 seconds in an hour. 5280/3600=22/15.