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

Pat - You are right. That's why this solution would satisfy both "dinosaurs" and contemporaries. :)

.btnCont {
  display: table-layout;
  width: 500px;
}

.txtCont {
  display: table-cell;
  width: 70%;
  max-width: 80%;
  min-width: 20%;
}

.subCont {
  display: table-cell;
  width: 30%;
  max-width: 80%;
  min-width: 20%;
}

  

    Long text that will auto adjust as it grows. The best part is that the width of the container would not go beyond 500px!
  
  

    This column as well as the entire container works like a table. Isn't Amazing!!!