<div class="basis">
  <div class="item">1<br>flex-basis-200px</div>
  <div class="item">2<br>flex-basis-30%</div>
  <div class="item">3<br>flex-basis-auto</div>
</div>
.basis {
  display:flex;
  background-color: lightskyblue;
}

.item:nth-of-type(1) {
  flex-basis:200px;
}
.item:nth-of-type(2) {
  flex-basis:30%;
}
.item:nth-of-type(3) {
  flex-basis:auto;
}

.item {
  background-color: red;
  color:#fff;
  margin: 10px;
  text-align: center;
  padding: 10px;
}

External CSS

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External JavaScript

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