<div class="wrapper">
  <div class="gold">
    <code>flex-basis: auto;</code>
  </div>
  <div class="red">
    <code>flex-basis: 175px;</code>
  </div>
  <div class="blue">
    <code>flex-basis: 45%;</code>
  </div>
</div>
* {
  box-sizing: border-box;
}

.wrapper {
  font-family: monospace;
  color: #fff;
  border: 2px solid #ddd;
  display: flex;
  margin-bottom: 36px;
} 

.wrapper > div {
  padding: 16px;
  text-align: center;
}

.gold {
  background-color: gold;
  flex-basis: auto;
}

.red {
  background-color: red;
  flex-basis: 175px;
}

.blue {
  background-color: steelblue;
  flex-basis: 45%;
}

External CSS

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External JavaScript

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