Siend,
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8" />
<title>ГГ</title>
<style>
.container div {
width: 100px;
height: 100px;
background-color: red;
}
.container {
width: 100%;
height: auto;
background-color: transparent;
border: 1px solid green;
text-align: center;
display: flex;
flex-wrap: nowrap ;
justify-content: space-between;
}
body{
margin: 0;
padding: 0;
}
</style>
</head>
<body>
<div class="container">
<div class="div1">первый</div>
<div class="div2">второй</div>
<div class="div3">третий</div>
</div>
</body>
</html>