Expand a div to fill the remaining width

Question

I want a two-column div layout, where each one can have variable width e.g.

Answer 1

You can use W3's CSS library that contains a class called rest that does just that:

  

    
150px
  
  

    
w3-rest
  

Don't forget to link the CSS library in the page's header:

Here's the official demo: W3 School Tryit Editor