I want to write down some equations, with some commentary between the equations. However, the equations need to be aligned and I want the commentary to be aligned to the left. My code is:
\begin{document}
\begin{align}
a+c&= b +d\\
a&= b+ d-c\\
\mbox{text at the left}\\
0&=b+d - a-c
\end{align}
\end{document}
Is this possible within the align environment?

\intertext{}is the command you are looking for. – darthbith Nov 04 '14 at 13:34