$\begin{array}{l} x=\left( \begin{array}{c} n +k-1 \\ k \end{array} \right) = \frac{(n+k-1)!}{(n-1)!\cdot k!}\\\\ \\ \left( \begin{array}{c} n +k-1 \\ k \end{array} \right) \\ \textbf{Gegeben:} \\ x=\left( \begin{array}{c} 6 +3-1 \\ k \end{array} \right) = \frac{(6+3-1)!}{(6-1)!\cdot 3!}\\\\x=\#x\\ \\ \textbf{Rechnung:} \\x=\left( \begin{array}{c} 6 +3-1 \\ k \end{array} \right) = \frac{(6+3-1)!}{(6-1)!\cdot 3!}\\\\x=56\\\\ \end{array}$