\documentclass[fleqn]{book}

\usepackage{xepersian}
\setlatinmonofont[ExternalLocation,BoldFont={pcrb8a},ItalicFont={pcri8a},BoldItalicFont={pcrbi8a}]{pcrr8a} 
\begin{document}
\begin{LTR}
\texttt{Farschad \%}

\[
\mathtt{Farschad \%} 
\]
\end{LTR}

\end{document}