سلام
برای رسم خط افقی، میتونین از \hrule استفاده کنین. کدتون رو کمی تغییر دادم که خلوتتر بشه.
\documentclass{article}
\usepackage{tabularx}
\usepackage{booktabs}
\begin{document}
	\begin{tabularx}{\textwidth}{p{.7\linewidth}|X@{}}
		\toprule\vskip0ex
		{\centering \textbf{Abstract}\vskip1ex}
		The concept of zero divisor graph of a ring was introduced by Beck in his study
		on the coloring problem of a commutative ring \cite{2}.
		He considered a ring $R$ as the vertex set of a graph $G(R)$.
		Two distinct vertices $x$ and $y$ of $G(R)$ are defined to be adjacent
		if and only if $xy = 0$.  Anderson and Livingston \cite{1},
		considered the set of all non-zero zero divisors as the vertex set to
		simplify the Beck's zero divisor graph. The edges can be defined in a similar
		way as Beck's seminal paper. This graph is denoted by $\Gamma(R)$.
		In this paper we use the Anderson-Livingston's definition of zero
		devisor graph and
		\begin{flushright}
			© 2022 University 
		\end{flushright} & \vskip0ex
		\begin{minipage}[t]{\linewidth}\raggedright
			\textbf{Keywords:}\\[1ex]
			{\footnotesize Text,\\ Other,\\ Some,\\ Example}
			\vskip2ex
			\hrule
			\vskip2ex
			\textbf{AMS Subject Classification (2020):}\\[1ex]
			{\footnotesize 05C50; 94B05; 05B05}
			\vskip2ex
			\hrule
			\vskip2ex
			\textbf{Article History:}\\[1ex]
			{\footnotesize Received: 07 August 2022,\\ Accepted: 11 November 2022,}
		\end{minipage}
	\end{tabularx}
\end{document}
