jmc

$$\begin{array}{rl}\left(\genfrac{}{}{0ex}{}{n}{n-1}\right)& =\frac{n!}{(n-1)!1!}\\ & =\frac{n\times (n-1)\times (n-2)\times (n-3)\times \cdots \times 2\times 1}{(n-1)\times (n-2)\times (n-3)\times \cdots \times 2\times 1}\\ & =\boxed{n}.\end{array}$$Also, $\left(\genfrac{}{}{0ex}{}{n}{n-1}\right)$ is the number of ways to choose $n-1$ objects out of $n$. This is equivalent to choosing $1$ object not to use. Since there are $n$ different objects, there are $\boxed{n}$ ways to do this.