Bootstrap 4

HTML

<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css">
<div class="container">
    <div class="row bg-primary d-flex justify-content-center">
      <div class="col-auto">
          LEFT
      </div>
      <div class="col-auto flex-grow-1 text-center">
          Middle
      </div>
      <div class="col-auto">
          Right
      </div>
    </div>
    
    <hr/>
    
    <div class="row bg-primary d-flex justify-content-center">
      <div class="col-auto">
          LEFT
      </div>
      <div class="col-auto flex-grow-1 text-center">
          Middle
      </div>
    </div>
</div>

CSS

body {
    margin: 10px;
    color: white;
}