JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li>20% - 60%</li>
    <li>32% - 75%</li>
    <li>82% - 95%</li>
    <li>12% - 49%</li>
    <li>42% - 100%</li>
</ul>

CSS

.bold {
    font-weight: bold;
}

JavaScript

jQuery.expr[":"].withinNum = function (el, i, m, num) {
    str = $(el).text();
    var min = parseInt(str, 10),
        max = parseInt(str.substr(-4), 10);
    return m[3] >= min && m[3] <= max;
};
$("li:withinNum(50)").addClass('bold');