\documentclass[10pt,reqno]{amsart}
\usepackage{amsmath,amssymb,amsthm}
\begin{document}
\section{Here are the fixmes}
\label{sec:first-one}

%<*1>
First fixme:
\begin{equation*}
  \int f dx
\end{equation*}
%</1>


%<*2>
Second  fixme:
%</2>


\end{document}