I need help please

Question

Carly loves to run while Riley prefers walking. Carly can run 3 miles per hour faster than her sister Riley can walk the same distance. If Carly ran 15 miles in the same time it took Riley to walk 9 miles, which equation can be used to find the speed of each sister?

Answer 1

distance = rate of speed times time

d=rt

t=d/r = 15/C = 9/R C=3+R

15/(3+R) = 9/R, solve for R

15R = 9(3+R) = 27 + 9R

6R = 27

R = 27/6 = 4.5 mph for Riley's speed

C = 7.5 mph for Carly

15/7.5 = 9/4.5 = 2 hours