Consider:
\documentclass[12pt, a4paper]{report}
\usepackage{amsfonts, graphicx, verbatim, mathtools,amssymb, amsthm, mathrsfs,amsmath}
\usepackage{tikz}
\begin{document}
\begin{figure}
\begin{subfigure}[h]{0.475\linewidth}
\includegraphics[width=\linewidth]{1SAIRSI.pdf}
\end{subfigure}
\hfill
\begin{subfigure}[h]{0.475\linewidth}
\includegraphics[width=\linewidth]{1SAIRSII.pdf}
\end{subfigure}\\[1ex]
\begin{subfigure}[h]{0.475\linewidth}
\includegraphics[width=\linewidth]{1SAIRSIII.pdf}
\end{subfigure}
\setlength{\textfloatsep}{10pt plus 1.0pt minus 2.0pt}
\caption{Plot of system (4.1)-(4.4) with $\beta_A=0.2$, $\beta_I=0.1$, $b=0.55$, $\mu=0.01$, $\nu=0.8$, $\rho=0.1$, $\xi =0.001$, $\gamma_A =0.15$, $\gamma_I=0.1$, $\sigma=0.2$, $\eta=0.7$ and $\alpha=0.01$ hence $\mathcal{R}_0 \approx 0.9265$.}
\setlength{\textfloatsep}{10pt plus 1.0pt minus 2.0pt}
\end{figure}
\end{document}
How do I flip the above MWE so its of the form:
x
x|x


example-image). A better sketch, what you like to get would be very helpful :-) – Zarko Jun 08 '22 at 13:07