Two divs side by side - Fluid display

Question

I am trying to place two divs side by side and using the following CSS for it.

#left {
  float: left;
  width: 65%;
          


        

Answer 1

This is easy with a flexbox:

#wrapper {
  display: flex;
}

#left {
  flex: 0 0 65%;
}

#right {
  flex: 1;
}

<div id="wrapper">
  <div id="left">Left side div</div>
  <div id="right">Right side div</div>
</div>

Answer 2

#sides{
margin:0;
}
#left{
float:left;
width:75%;
overflow:hidden;
}
#right{
float:left;
width:25%;
overflow:hidden;
} 

<h1 id="left">Left Side</h1>
<h1 id="right">Right Side</h1>
<!-- It Works!-->