%note: run "Quick Build" twice.

\documentclass[a4paper,12pt]{article}
\usepackage{tkz-linknodes}

%when uncomment this line, makes error.
%\usepackage[Kashida]{xepersian}



\begin{document}

 \begin{NodesList}[margin=4 cm]
\begin{displaymath}
\begin{aligned}
2x &= 8 \AddNode\\
x &= 4 \AddNode 
 \end{aligned}
\end{displaymath}

 \LinkNodes{$\div 2$}
 \end{NodesList}
 
 \end{document}