In this question, we are selecting 2 people to create a dance pairing, and the order of the 2 selected people does not matter (for example, selecting A and B to be a pair is the same as selecting B and A).
Since the order does not matter here, this is a combination question.
We can select/choose 2 people from x people in xC2 different ways (this notation, xC2, can be read as "x choose 2") where xC2 = x!/(x-2)!(2!)
From here, we should plug different values of x (2, 3, 4, 5, etc) until we find an output that matches one of the answer choices.
To learn a quick way to calculate combinations in your head, you can watch this video:
https://youtu.be/-bbu2h-07iA
Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
