Answer: 504
Step-by-step explanation:
First of all, there are 3 places.
_ _ _
In the first place, any of the 9 horses can be first.
9 _ _
Now, 8 horses are remaining. You can put any of those 8 horses in second place.
9 8 _
Finally, 7 horses are remaining. You can put any of those 7 horses in third place.
9 8 7
We multiply these numbers to find ways horses can be 1st, 2nd or 3rd in race.
= 9 × 8 × 7
= 504
