<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
* {
margin: 0px;
padding: 0px;
}
section {
width: 100%; background: lightcyan; display: flex;
}
section article {
width: 100px; height: 100px; background: aqua; border: 1px solid #000; font-size: 50px; color: white;
}
@media all and (max-width:600px) {
section article:nth-of-type(1) { flex-grow: 1;}
section article:nth-of-type(2) { flex-grow: 1;}
section article:nth-of-type(3) { flex-grow: 1;}
}
</style>
</head>
<body>
<main>
<section>
<article>1</article>
<article>2</article>
<article>3</article>
</section>
</main>
</body>
</html>
