How many ways can a group of 12 choose a committee of 9?

Nine people can be selected from the group of 12 in

(12 x 11 x 10 x 9 x 8 x 7 x 6 x 5 x 4) = 79,833,600ways.

But each group of the same 9 people can be selected in

(9 x 8 x 7 x 6 x 5 x 4 x 3 x 2) = 362,880 different orders.

So the number of different 9-person committees that can be selected is

79,833,600/362,880 = 220 .