JSFiddle - React, Tailwind, and code Playground

HTML

<div class="wrapper">
<div class="line">
</div>
<select class="select1">
<option>1</option>
<option>2</option>
</select>
<select class="select2">
<option>1</option>
<option>2</option>
</select>
</div>

CSS

.wrapper{
  position:relative;
}

.select2, .select1{
  height:20px;
  width:40%;
  position:absolute;
}

.select1{
  left:0;
}

.select2{
  right: 0;
}

.line{
  position:absolute;
  border-bottom: 1px solid red;
  top:10px;
  left:0;
  right:0;
}