mozna bych to zkusil obejitim \newenvironment
\def\ex{
\setcounter{buf}{\arabic{equation}}
\setcounter{equation}{0}
\makeatletter
\def\theequation{Ex.\arabic{pr}.\@arabic\c at equation}
\makeatother
}
\def\endex
{
\setcounter{equation}{\arabic{buf}}
%\end{pr} < kde to ma begin?
}
bohuzel jsem nenasel \begin{pr}, ani \end{equation}
arnost