Displaying math equations and formulas are pretty simple and easy. MathJax is latex based tool that allows to enter them in webpages and posts.

To display this equation R=\frac{E}{I} we put $$ symbol at the beginning and the end of the equation.

$$R=\frac{E}{I}$$

It will be displayed after the page gets done loading

To see all the ways latex can be used see attached pdf file