JSFiddle - React, Tailwind, and code Playground

HTML

<div>
    <input type="text"  class='save'/>
    <input type="button" value="Save" />
</div>
<br>
<div>
    <input type="text" class='dns' />
    <input type="button" value="Do not Save" />
</div>

CSS

div{
    width:200px;
    background-color:orange;
    
}
.dns{
    width:calc(100% - 105px)
}
.save{
    width:calc(100% - 65px)
}
div>input[type='button']{
  float:right;
}