Normal Wiki text followed by a formula

{{mathjax}}
\begin{eqnarray}
1 & = & a x + b y\label{eq:first} \\
0 & = & c x + d y\label{eq:second}
\end{eqnarray}
{{/mathjax}}

Solving equation {{mathjax}}\ref{eq:second}{{/mathjax}}, for {{mathjax}}x{{/mathjax}}, and substituting back into equation {{mathjax}}\ref{eq:first}{{/mathjax}}, yields

{{mathjax}}
\begin{equation}
y = \frac{c}{cb-ad}
\end{equation}
{{/mathjax}}