Answer:
6840 I think.
Explanation:
There's 20 people in the race, it's asking for how many possibilities there are for each person to end up as 1st, 2nd, & 3rd.
Problems like these are solved by 20! (20x19x18xetc till 1) over (the number of competitors (20) minus the number of prized places (3)). 20-3=17.
20! over 17!.
Sorry if it's wrong but it's how I remember it to be.