JSFiddle - React, Tailwind, and code Playground

HTML

<div class="cont">
<div>бла бла бла </div>
<div class="contwr100"></div>
<div>500</div>
</div>

CSS

.cont{
display: flex;
}
.contwr100{
  flex-grow: 1;
  border-bottom: 2px dotted red;
}