div
{
  padding: 20px;
  margin: 5px;
  float: left;
}

#parent-div
{
  width: 500px;
  background: red;
}

#box-one
{
  background: lime;
  width: 70px;
}

#box-two
{
  background: blue;
  width: 70px;  
}

#box-three
{
  background: beige;
  width: 70px;
}