## Precalculus (6th Edition) Blitzer

The value of the provided expression $_{13}{{C}_{11}}$ is $78$
We plug the values into the combination formula: \begin{align} & _{13}{{C}_{11}}=\frac{13!}{11!\left( 13-11 \right)!} \\ & =\frac{13!}{11!2!} \\ & =\frac{13\times 12\times 11!}{2\times 11!} \\ & =78 \end{align}