what do the letter mean

$${\mathtt{2}}{\mathtt{\,\small\textbf+\,}}{\mathtt{x}} = {\mathtt{5}}{\mathtt{\,\times\,}}{\mathtt{X08}}{\mathtt{\,-\,}}{\mathtt{66}}{\mathtt{\,\small\textbf+\,}}{\mathtt{45}}{\mathtt{\,\times\,}}{\mathtt{ytyty}} \Rightarrow {\mathtt{x}} = {\mathtt{45}}{\mathtt{\,\times\,}}{\mathtt{ytyty}}{\mathtt{\,\small\textbf+\,}}{\mathtt{5}}{\mathtt{\,\times\,}}{\mathtt{x08}}{\mathtt{\,-\,}}{\mathtt{68}}$$