\documentclass{article} \newcounter{saveeqn} \newcounter{prenum} \newcommand{\vareqn}[2]{\setcounter{saveeqn}{\value{equation}}% \setcounter{equation}{0}\setcounter{prenum}{#1} \renewcommand{\theequation}{\arabic{prenum}[#2{equation}]}} \newcommand{\reseteqn}{\setcounter{equation}{\value{saveeqn}}% \renewcommand{\theequation}{\arabic{equation}}} \begin{document} \setcounter{equation}{9} \vareqn{33}{\Alph} \begin{equation} \frac{a^2 - b^2}{a + b} = a - b \end{equation} \begin{equation} \sqrt[3]{-q + \sqrt{q^2 + p^2}} \end{equation} \begin{equation} \sqrt[n]{\frac{x^n - y^n}{1 + u^{2n}}} \end{equation} \reseteqn \begin{equation} 2\sum_{i=1}^n a_i \int^b_a f_i(x) g_i(x)\,dx \end{equation} \end{document}