Answer:
24
Explanation:
Start with 90 runners.
1/3 dropped out.
1/3 of 90 = 1/3 * 90 = 30
30 runners dropped out.
90 - 30 = 60
Now there are 60 runners.
3/5 of the remaining runners dropped out.
3/5 of 60 = 3/5 * 60 = 36
36 runners dropped out.
60 - 36 = 24
24 runners finished the race.