JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<title>Задание 1</title>
<body>
  <div class="box1">
    <p>66% родителя</p>
  </div>
  <div class="box2">
    <p>66% родителя</p>
  </div>
</body>

CSS

p {
  text-align: center;
  font: 20px;
  font-family: Geneva, Arial, Helvetica, sans-serif; 
  color: #000;
}

div {
  width: 66%;
  height: 100px;
  padding: 10px;
  margin: 10px;
  border: 1px solid #000;
}

.box1 {
  background: #ffff7f;
  margin-right: auto;
}

.box2 {
  background: #d8b2d8;
  margin-left: auto;
}