Question

At a benefit​ concert, nine bands have volunteered to perform but there is only enough time for six of the bands to play. How many lineups are​ possible?

Answer 1

You have to calculate how many ways you can select six things (r)
from a set of 9 things (n).  (See attached formula).

9! / 6! * (3!) =
9*8*7 * 6! / 6! * 3! =
9*8*7 / 3! =
3 * 4 * 7 = 84 lineups