JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
    <span class="fixed">FIXED WIDTH (110px)</span>
    <div class="varies">WIDTH VARIES WITH HEADER TEXT</div>
    <div class="right">WIDTH EXPANDS TO FILL REMAINING SPACE</div>
</div>

CSS

.container {
    overflow: hidden; /* clear the float */

}
.fixed {
    height: 50px;
    width: 110px;
    vertical-align:middle;
    float: left;
    border-radius:10px;
    background-color:red;
}
.varies {
    height: 50px;
    float: left;
    border-radius:10px;
    background-color:green;
}

.right {
    height: 50px;
    overflow: hidden;
    background-color: blue;
    border-radius:10px;
}