I want to typeset the Pascal expression

(chr='A') and (num=3)

in MathJax with the number, parentheses, equality sign and logical “and” operator rendered as mathematical symbols and the rest in typewriter font. I use the TeX commands hbox and tt to achieve this.

.a mjx-c.mjx-c2019::before {
  content: "27" !important;
  padding-right: 0.525em !important;
  font-family: MJXZERO, MJXTEX-T;
}

<script src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-chtml-full.js" type="text/javascript"></script>
<span class="math a">[(hbox{tt{chr}}=hbox{tt{'A'}})land
 (hbox{tt{num}}=3)]</span>
<span class="math b">[(hbox{tt{chr}}=hbox{tt{'A'}})land
 (hbox{tt{num}}=3)]</span>

It works, but I need the mysterious CSS style to have the single quotes come out in typewriter font.

Other characters inside a tt{...} come out in typewriter font correctly. Why are single quotes treated differently?