Answer
$15504$
Work Step by Step
The number of ways of selecting $n$ elements from $N$ elements is given by the combinations rule:
$$\binom{N}{n} = \dfrac{N!}{n! (N-n)!}$$
The number of ways of selecting 5 elements from 20 elements is given by
${\displaystyle{\binom{20}{5}}= \dfrac{20!}{5! \, (20-5)!}= \dfrac{20!}{5! \, 15!} = \boxed{15504}}$
