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?
subequations
must itself be enclosed in a math mode,$...$
,\(...\)
,\[...\]
,\begin{equation}...\end{equation}
, etc.