four out of 9 performers will be chosen to stand in a row on stage. how many ways can the 4 performers stand in a row? a. 362,880 ways b. 347,760 ways c. 15,120 ways d. 3024 ways

Imagine you have 4 'slots' on the stage:
_ _ _ _

In the first one there can be 1 out of 9 performers.
In the second - 1 out of 8 (because one has been already chosen).
In the third - 1 out of 7 (because two have been selected).
In the forth - 1 out of 6 (because three are already on the stage).

Total number of combinations is equal to: 9x8x7x6 = 3024

So the correct answer is D.

Hope it helps!