JSFiddle - React, Tailwind, and code Playground
HTML
<input type="radio" id="addweekhours" class="option-input radio" />
<span> First</span>
<div id="showweekhours" style="display:none;">
<input id="ChkSUN" type="checkbox" class="single sun option-input checkbox" name="days"/>
<span> Second</span>
</div>
JavaScript
$('#addweekhours').click(function () {
$('#showweekhours').slideToggle("fast");
});