JSFiddle - React, Tailwind, and code Playground

HTML

<div class="box1">66% родителя</div>
<div class="box2">66% родителя</div>

CSS

.box1, .box2 {
  box-sizing: border-box;
  border: 1px solid #8D8D8D;
  margin: 10px;
  height: 70px;
  width: 66%;
  text-align: center;
  line-height: 300%;
  color: #2F3F77;
}
.box1 {
  background-color: #FEFD8F;
}
.box2 {
  background-color: #F6CCFC;
  margin-left: auto;
}