JSFiddle - React, Tailwind, and code Playground

HTML

<div class="columns">
  <div class="column1 resizable">
    Resizable
  </div>
  <div class="column2">
    Flex 75%
  </div>
</div>

CSS

.columns {
  display: flex;
}

.columns > div {
  background: #aaa;
  padding: 10px;
  margin: 5px;
}

.resizable {
  width: 330px;
  overflow: auto;
}

.column1 {
  max-width: 150px;
}

.column2 {
  flex: 0.75 0 auto;
}