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Combitation

Discrete Mathematics Level 5

\[ \begin{eqnarray} ^{ x }{ { P } }_{ 2 } & =& 42 \\ (x-n)! & =& 120 \\ ^{ x }{ { C } }_{ n+3 } & =& \ ? \end{eqnarray} \]

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by Abdulrahman El Shafei

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