% use "latex" to generate a *.dvi file, and use "dvisvgm --no-fonts" to convert to .svg
\documentclass[tikz, border=5mm]{standalone}
\begin{document}
\begin{tikzpicture}[scale=0.5]
  \draw[fill=black!5] (-6.25,3) rectangle node {$U_n^*$} +(6,3);
  \draw[fill=black!5] (0,0) rectangle node {$A$} +(3,6);
  \draw[fill=black!5] (3.25,3) rectangle node {$X$} +(3,3);
  \node at (6.75,4.5) {=};
  \draw (7.25,3) rectangle +(3,3) (7.25,6) -- +(3,-3);
  \node[below] at (8.75,3) {$C$};
  \begin{scope}[yshift=-3.5cm]
  \draw[fill=black!5] (-2.25,1) rectangle node {$V_n^*$} +(2,2);
  \draw[fill=black!5] (0,1) rectangle node {$B$} +(3,2);
  \draw[fill=black!5] (3.25,0) rectangle node {$X$} +(3,3);
  \node at (6.75,1.75) {=};
  \draw (7.25,1) rectangle +(3,2) ++(3,0) -- +(-2,2);
  \node[below] at (8.75,1) {$S$};
  \end{scope}
\end{tikzpicture}
\end{document}
