Three runners, Dirk, Edith, and Foley all start at the same time for a $24$ km race, and each of them runs at a constant speed. When Dirk finishes the race, Edith is $10$ km behind, and Foley is $15$ km behind. When Edith finishes the race, how far behind is Foley, in km?
Edith runs 14 km in the time it takes Foley to run 9 km
Edith has 10 km to go to finish
10/14 = x/9 shows x = distance Foley covers while Edith finishes 6 3/7 km
so when Edith finishes , Folyey has covered 6 3/7 + 9 = 15 3/7 km and is thus 8 4/7 km behind Edith