<div class="container">
  <div class="container__el container__el--red"></div>
  <div class="container__el container__el--green"></div>
</div>

.container {
  width: 800px;
  height: 400px;
  max-width: 100%;
  background: #000;
}

.container__el {
  display: inline-block;
  width: 20%;
  height: 200px;
  border-radius: 50%;
}

.container__el--red {
  background: red;
}

.container__el--green {
  background: green;
}