JSFiddle - React, Tailwind, and code Playground

HTML

<div class="wrap">
    <div class="fluid wrap">
        <div class="fluid">
        </div>
        <div class="fixed">
        </div>
    </div>
    <div class="fixed">
    </div>
</div>

CSS

.wrap {
    display: -webkit-flex;
    display: -ms-flexbox;
    display: flex;
}
.wrap div {
    height: 5em;
    -webkit-flex: 1 1 auto;
    -ms-flex: 1 1 auto;
     flex: 1 1 auto;
}
.fluid {
    background: tomato;
    width: 100%;
}
.fixed {
    background: beige;
    width: 150px;
    min-width: 150px;
}
.fluid.wrap .fluid {
    background: orange;
}
.fluid.wrap .fixed {
    background:tomato;
}