does anybody know how this came from?
thank you
Actually, a (.) is used as a decimal point, it's actually a centred dot, $\displaystyle \displaystyle \begin{align*} \cdot \end{align*} $ which is used for multiplication. Though a $\displaystyle \displaystyle \begin{align*} \times \end{align*} $ is also acceptable as long as it doesn't get mixed up with any $\displaystyle \displaystyle \begin{align*} x \end{align*} $ variables.
The solution has already been given, but I thought I'd rewrite it a bit:
$\displaystyle \frac{8!}{4! \cdot 4!} + \frac{8!}{5! \cdot 3!} = \frac{8!}{4! \cdot 3!} \left ( \frac{1}{1 \cdot 4} + \frac{1}{5 \cdot 1} \right )$
We have a forum that deals with how to write expressions. It's the LaTeX Help forum. It's pretty easy to learn the basics.
-Dan