So in Jekyll and Markdown, I can\'t type $ or its HTML equivalent code, and not \\$ nor $\\$$. How should I type the dollar sign?
Enable processEscapes:
processEscapes
MathJax.Hub.Config({ tex2jax: { inlineMath: [['$','$'], ['\\(','\\)']], processEscapes: true } });
Then you can simply use \$ to get a plain $.
\$
$