MediaWiki uses a subset of AMS-LaTeX markup, a superset of LaTeX markup which is in turn a superset of TeX markup, for mathematical formulae. It generates either PNG images or simple HTML markup, depending on user preferences and the complexity of the expression. In the future, as more browsers become smarter, it will be able to generate enhanced HTML or even MathML in many cases.
3 x 2 = 6 can be displayed as <math>{3 ~ \times ~ 2 ~ = ~ 6}</math> to generate
Notes
Large formulas may become wider than the page width allowed by Wikia' wikis and will overlap the right hand side-rail information, if your math formula is near the top of the page you wish to use.
One solution is to place the formula inside of a simple basic table, with no borders or anything.
Tables, that get to wide, will show the Pop-Out button, so that the whole table can be seen. Here is an example: