JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Checkbox</title>
</head>
<body>
<div class="wrapper">
    <div class="menu">
        <div class="left">
            <input type="button" disabled="true" value="Оплатить" id="but">
        </div>
        <div class="right">        
            <input type="checkbox" name="ch1" onchange="checkitout(this, 'but');" value="ch1"> check me!
        </div>
        <div style="clear: both;"></div>
    </div>
</div>
</body>
</html>

CSS

body
    {
        margin: 0;
        padding: 0;
        background: #FFFEFB;
    }
    .wrapper
    {
        width: 500px;
        margin: 0px auto;
        padding: 200px  0 0 0;
        position: relative;
    }
    .menu
    {
        width: 500px;
    }
    .left
    {
        float:left;
    }
    .right
    {
        float:left;
    }

JavaScript

function checkitout(elem, dis)
    {
        if(elem.checked)
        {
            document.getElementById(dis).disabled = false;
        }
        else
        {
            document.getElementById(dis).disabled = true;
        }
    }