Answer:
80mph
Explanation:
you add the time which is 3 and 2 1/4 hours. Then you look at the equation d = r/t. d = distance, r = rate, and t = time. Then you put them in there places like this, 420 = (2 1/4 + 3)/ r. 2 1/4 + 3 = 5.25. Then 420/5.25 to get 80 mph