Since the president is selecting 3 cabinet members from 8 but the order of selection is not going to matter since all of the candidates can server any position, this situation can be represented as a combination
[tex]8C3[/tex]Applying the formula of combinations
[tex]\begin{gathered} \text{nCr}=\frac{n!}{(n-r)!r!} \\ 8C3=\frac{8!}{5!3!} \\ 8C3=56 \end{gathered}[/tex]