<style>
  #box-container {
    background: gray;
    display: flex;
    height: 500px;
    
  }
  #box-1 {
    background-color: dodgerblue;
    width: 200px;
    font-size: 24px;
  }

  #box-2 {
    background-color: orangered;
    width: 200px;
    font-size: 18px;
  }
</style>

<div id="box-container">
  <div id="box-1"><p>Hello</p></div>
  <div id="box-2"><p>Goodbye</p></div>
</div>