# Factorial fun!

Number Theory Level 2

Suppose that $$n!!$$ is defined as follows:

$n!! = \begin{cases} n \times (n-2) \times \cdots \times 5 \times 3 \times 1 &\text{if } n \text{ is odd.} \\ n \times (n-2) \times \cdots \times 6 \times 4 \times 2 &\text{if } n \text{ is even.} \\ 1 &\text{if } n = 0, - 1. \\ \end{cases}$

Then what is

$\color{red}{\dfrac{9!}{6!!}} \div \color{green}{\dfrac{9!!}{6!}}?$

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