/* style-test.css */
.two-cols {
display:flex;
}
.col-1, .col-2 {
flex:1;
border:1px solid green;
}<!-- test.html -->
<!DOCTYPE html>
<html lang="en">
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet"
href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
<link rel="stylesheet" href="css/style-test.css">
</head>
<body>
<div class="two-cols">
<div class="col-1">
Bootstrap HTML, CSS, and JavaScript framework
Bootstrap HTML, CSS, and JavaScript framework
Bootstrap HTML, CSS, and JavaScript framework
Bootstrap HTML, CSS, and JavaScript framework
Bootstrap HTML, CSS, and JavaScript framework
</div>
<div class="col-2">
</div>
</div>
</body>
</html>