JSFiddle - React, Tailwind, and code Playground

HTML

<input type="checkbox" /><br />
<div>100</div>

JavaScript

$(function() {
    
    var div  = $('div');
    
    $('input').click(function() {
        if($(this).is(':checked')) {
            div.html(div.text() += 49);    
        } else {
            div.html(div.text() -= 49);      
        }
    });
    
});