\documentclass[10pt]{bidipresentation}
\usepackage{amsmath,amssymb}
\usepackage{xepersian}
\settextfont{Yas}
\setdigitfont{Yas}

\linespread{2}
\pagestyle{pres}
\begin{document}
%%%%%%%%%%%%%%%%%%%%%%
\begin{plainslide}
\begin{align}
&   aaaaaaaaaaaa 
\end{align}

\begin{equation}
 bbbbbbbbbbbbbbb
\end{equation}
\end{plainslide}
%%%%%%%%%%%%%%%%%%%%%%


\end{document}