JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">
    <div id="left"><%= render 'form' %></div>
    <div id="right"><%= render 'totals' %></div>
</div>

CSS

body {
  margin: 0;
}
#container {
        display: block;
        font-size: 0;
        margin-left: auto;
        margin-right: auto;
        text-align: center;
}
#left, #right {
  display: inline-block;
  font-size: 16px;
}
#left {
        background-color: green;
}
#right {
        background-color: red;
}