Increment/display the content of a (variable)/(section number) under latex?

Question

To have something equivalent to echo of the shell. For instance in .tex file we have:

 \def \var{2}

    The content of var is $var

How to edit the tex file in such a way we have as output:

The content of var is 2?

Especially, can we perform arithmetic operations under latex? Say

var = var + x

Answer 1

% arara: pdflatex

\documentclass{article}
\newcommand*{\var}{2}
\newcommand*{\x}{5}

\begin{document}
    The content of \verb|\var| is \var

    $\var+\x = \the\numexpr\var+\x\relax$
\end{document}

---

Edit:

In your comment to your question, you ask something quite different. This could be done like this:

% arara: pdflatex

\documentclass{article}
\newcounter{mycounter}

\begin{document}
    \setcounter{mycounter}{42}
    \themycounter{} My Section Starting where I Want
    \stepcounter{mycounter}

    \themycounter{} And Here Comes the Next Section 
\end{document}