You can enter fractions and other mathematical symbols in a WordPress blog (see this page for an explanation of how to get started). I’ve taught students as young as grade 6 how to use simple LaTeX. Here’s an example of a fraction.
You can write more complicated formulas and have them render in WordPress. Here are a couple of more complicated examples (thanks to John Forkosh for the LaTeX code). If you need to figure out what LaTeX code to use, check out this online equation editor from Code cogs.
You can use Google’s Chart Wizard to add graphs (many different kinds available) to your posts. See this graph for example:
Update: The image above is broken because of some weird secure https caching mechanism WordPress.com is using. This will work fine on a personal blog, or you can just save the Google Charts image to your desk and upload it to WordPress.com