<div class="wrapper">
  <div class="box1">% Specified</div>
  <div class="box2">%Specified</div>
  <div class="box3">%Specified</div>
</div>
.wrapper{
  width: 100%;
  font-size: 12px;
}
.wrapper div{
  /*width 100% divided by 3*/
  width: calc(100% / 3);
  height: 50px;
  text-align: center;
  line-height: 50px;
  float: left;
}
div.box1{
  background: #aadebb;
}
div.box2{
  background: #ded0aa;
}
div.box3{
  background: #e4c4ef;
}

External CSS

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External JavaScript

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