%%
%% The LaTeX Companion, 3ed
%%
%% Example A-5-1 on page II-687 in "calc --- Arithmetic calculations".
%%
%% Copyright (C) 2022 Frank Mittelbach
%%
%% It may be distributed and/or modified under the conditions
%% of the LaTeX Project Public License, either version 1.3c
%% of this license or (at your option) any later version.
%%
%% See https://www.latex-project.org/lppl.txt for details.
%%

\documentclass{tlc3exa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{135.0pt}
%StartShownPreambleCommands
\usepackage{csquotes,calc}
\newcounter{private}
\setcounter{private}{2} % initial setting for the example
%StopShownPreambleCommands

\begin{document}
The value is currently \enquote{\theprivate}.\\
\setcounter{private}{\value{private}*2 + 5}
The value has now changed to \enquote{\theprivate}.
\end{document}