MathJax.Hub.Config({
    jax: ["input/TeX","output/HTML-CSS"],
    displayAlign: "left"
});

.MathJax_Display {
  text-align: left !important;
}

.MathJax_Display {
    text-align: left !important;
    display: inline !important;
}

<div class="math-left-align">
    $$ a + b = c $$
</div>

.math-left-align .mjx-chtml.MJXc-display{
    text-align: left !important;
 }