[salamanderjuice]

MathML only works for Kepubs.

This code works fine on my Kobo Libra Colour:

<p><math display="block" xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mo stretchy="true" form="prefix">[</mo><mtable><mtr><mtd columnalign="center"><mn>1</mn></mtd><mtd columnalign="center"><mn>2</mn></mtd></mtr><mtr><mtd columnalign="center"><mn>2</mn></mtd><mtd columnalign="center"><mn>0</mn></mtd></mtr><mtr><mtd columnalign="center"><mn>3</mn></mtd><mtd columnalign="center"><mn>1</mn></mtd></mtr></mtable><mo stretchy="true" form="postfix">]</mo></mrow><annotation encoding="application/x-tex">\begin{bmatrix}
 1 &amp; 2 \\[0pt]
 2 &amp; 0 \\[0pt]
 3 &amp; 1 \\[0pt]
\end{bmatrix}</annotation></semantics></math></p>

Is this a book you bought or generated? I'm not sure if there is an easy fix if this is a problem throughout.