Distance/ time word problem

Question

Fiora starts riding her bike at 20 mph. after a while she slows down to 12 mph and maintains that speed for the rest of teh trip. the whole trip was 70 miles taking 4.5 hours. for what distance does she travel 20 mph

Answer 1

70/4.5 = =140/9 = 15 5/9 mph = average speed for the full trip

d=rt

distance = rate of speed times time

20x + 12(4.5-x) = 70

20x-12x = 70 - 54

8x = 16

x = 16/8 = 2 hours at 20 mph

and 2.5 hours at 12 mph