# Missing $inserted error when using \frac inside subequations environment? Here's a MNWE (minimum not working example): \documentclass[12pt,letterpaper]{article} \usepackage{amsmath} \usepackage{amsthm} \usepackage{amsfonts} \usepackage{amssymb} \begin{document} \section{Hello World} \begin{subequations} \frac{a}{b} = 0 \\ \end{subequations} \end{document}  The errors: line 12: Missing$ inserted \frac{a}{b}
line 12: Extra }, or forgotten $\frac{a}{b} line 13: Missing$ inserted \end{subequations}
line 13: Missing } inserted \end{subequations}


How do I fix the MNWE?

• It would appear that subequations must itself be enclosed in a math mode, $...$, $$...$$, $...$, $$...$$, etc. Dec 20, 2014 at 20:57

subeequations does not in itself start math math mode, but all numbered equations within it will be numbered as 1a, 1b, etc. The environment can also contain text.

\documentclass[12pt,letterpaper]{article}

\usepackage{amsmath}
\usepackage{amsthm}
\usepackage{amsfonts}
\usepackage{amssymb}

\begin{document}

\section{Hello World}
\begin{subequations}
Here is some text.
$$\frac{a}{b} = 0$$
Then follows some more text, followed by some more equations.
\begin{gather}
a=b \\
c = d
\end{gather}
\end{subequations}

The next equation is not part of the subequations.
$$g=h$$
\end{document}