\documentclass{article}
\usepackage{latexml}
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\section{Basic math}
\[ a + b + c - d + e \]
\[ a + b c - d  e \]
\[ a b c / d e \]
\[ a \times b \times c / d \times e \]

\paragraph{N-ary special cases}
\[ a \times b \times c \times d \]
\[ (a \times b) \times (c \times d) \]
\[ ((a \times b) \times (c \times d)) \]

\[ a / b / c \]
\[ \frac{a}{b} / c \]
\[ a / \frac{b}{c} \]

\[ a \times \fbox{$b \times c$}\]
\end{document}