Chapter 8.1, Problem 87PE

During a race, Marta bicycled 12 mi and ran 4 mi in a total of $1\text{hr}20\text{min} \left(\frac{4}{3}\text{hr}\right).$ In another race, she bicycled 21 mi and ran 3 mi in $1\text{hr}40\text{min}\left(\frac{5}{3}\text{hr}\right)\text{.}$ Determine the speed at which she bicycles and the speed at which she runs. Assume that her bicycling speed was the same in each race and that her running speed was the same in each race.