The following columns are always 50% wide, on mobile and desktop.
<!DOCTYPE HTML>
<html>
<head>
<link href="http://java2s.com/style/bootstrap.min.css" rel="stylesheet">
<style>div{background:#eee;border:1px solid #DDD;}</style>
</head><!--from w w w .ja va2 s . c om-->
<body style='margin:20px;'>
<div class="row">
<div class="col-6 col-lg-6">6</div>
<div class="col-6 col-lg-6">6</div>
</div>
<div class="row">
<div class="col-lg-3 col-lg-offset-3">3 offset 3</div>
<div class="col-lg-3 col-lg-offset-3">3 offset 3</div>
</div>
<div class="row">
<div class="col-lg-6 col-lg-offset-3">...</div>
</div>
</body>
</html>