除数不是太突出:
\documentclass{article}
\usepackage{amsmath,mathtools}
\newcommand{\fracdiv}[3]{%
\frac{#1\mathrlap{\scriptstyle\div#3}}
{#2\mathrlap{\scriptstyle\div#3}}%
\hphantom{\scriptstyle\div#3}%
}
\begin{document}
\[
\fracdiv{27}{18}{9}=\frac{3}{2}
\]
\end{document}