To have an expression evaluated by Mathjax you’ll have to first include the shortcode somewhere on the page. This will allow for loading the Mathjax scripts, but only for those pages that include the shortcode. Then place the expression between the correct escape sequences. For inline display these are slashes followed by an open bracket to start and a slash followed by a close bracket to finish. This is rendered by Mathjax \(E=mc^2\)
Fractions are easy with Mathjax as well. Thirty forty-fourths are easily expressed. The expression is “30 \over 44” which is rendered as \(30 \over 44\). Of course the fraction command itself is even easier, “\frac{30}{44}” gives the same result \(\frac{30}{44}\)
Personally I prefer the display of limits above and below the integral. Use the \limits command to achieve this effect: “\int\limits_0^{2\pi}” renders as \(\int\limits_0^{2\pi}\)