Explanation:
This is a question that bothers combination. Combination has to do with selection.
When selecting r objects out of a pool of n objects, the number of ways this can be done is:
nCr = n!/(n-r)!r!
If a local BBQ restaurants offers 2 side dishes with a lunch plate, and there are 7 side dishes, the number of choices that the customer have is expressed as:
7C2 = 7!/(7-2)!2!
7C2 = 7!/(5)!2!
7C2 = 7*6*5!/5! * 2
7C2 = 7*6/2
7C2 = 42/2
7C2 = 21 choices
Hence the customer has 21 choices of side dishes to make