\documentclass[a4paper,11pt]{article}
\usepackage{xepersian}
\settextfont[Scale=1.1]{XB Niloofar}
%\setlatintextfont[Scale=1.1]{XB Niloofar}
\setdigitfont[Scale=.85]{Persian Modern}

\begin{document}
\begin{flushleft}
\begin{itemize}
\item[] $A=\{2,4,6,8,...\}$
\item[] $B=\{\sqrt{x}\mid x\in\mathcal{N},x\leq 7\}$
\end{itemize}
\end{flushleft}
\end{document}