Answer
The required solution is ${}_{n}{{C}_{r}}=\frac{n!}{r!\left( n-r \right)!}$
Work Step by Step
We know that the above problem uses combinations as the order of the selection does not matter.
The formula is given by:
${}_{n}{{C}_{r}}=\frac{n!}{r!\left( n-r \right)!}$
