SOURCE

<div class="box">
  <div class="left">left</div>
  <div class="right">right</div>
  <div class="center">center</div>
</div>

.box {
  
}

.left {
  float: left;
  width: 100px;
  border: 1px solid red;  
}

.center {
  margin-right: 105px;
  margin-left: 105px;
  border: 1px solid blue;
}

.right {
  float: right;
  width: 100px;
  border: 1px solid green;
}