JSFiddle - React, Tailwind, and code Playground

HTML

<div id="wrapper">
		<div id="alleft">
			Левый блок
		</div>
		<div id="alright">
			Правый блок
		</div>
</div>

CSS

#wrapper {
    border-style: solid;
    border-width: 1px;
    padding: 10px;
    text-align: justify;
}
#wrapper:after {
  content: "";
  display: inline-block;
  width: 100%;
  height: 0;
  visibility: hidden;
  overflow: hidden;
}

#alleft {
  background-color: yellow;
  width: 40%;
  margin-bottom: 5px;
  display: inline-block;

}
#alright {
  background-color: red;
  width: 40%;
  margin-bottom: 5px;
  display: inline-block;
}