Here is a simple solution to put math equation in jekyll website.
First put the following javascript in _layouts/post.html
<script type="text/javascript"
src="http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML">
</script>Then try display a math expression.
Use \\( ... \\) like \\( sin(x^2) \\) to create inline equation \( sin(x^2) \).
I hope this is useful.
Reference: MathJax with Jekyll