flex - three columns

https://www.w3schools.com/cssref/tryit.asp?filename=trycss3_flex

by Andy Bulka

HTML

<div id="main">
  <div style="background-color:coral;">RED</div>
  <div style="background-color:lightblue;">BLUE</div>  
  <div style="background-color:lightgreen;">Green div with more content.</div>

  <textarea rows="140">
  At w3schools.com you will learn how to make a website. We offer free tutorials in all web development technologies.
  </textarea>

</div>

CSS

#main {
    width: auto;
    height: 200px;
    border: 1px solid black;
    display: flex;
}

#main div {
    flex: 1;
}