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13! (13−4)!4!

$\begin{array}{|rcll|} \hline && \frac{13!}{(13-4)!4!} \\ &=& \dbinom{13}{4} \\ &=& \frac{13}{4}\cdot \frac{12}{3}\cdot \frac{11}{2}\cdot \frac{10}{1} \\ &=& \frac{13}{1}\cdot \frac{12}{12}\cdot 11 \cdot \frac{10}{2} \\ &=& 13\cdot 1\cdot 11\cdot 5 \\ &=& \mathbf{715} \\ \hline \end{array}$

13! / (13−4)!4! =6,227,020,800 / [362,880 x 24] =715