JSFiddle - React, Tailwind, and code Playground
HTML
<input type="text" name="subject2" id="sub2" class="i2" size="20" disabled> <br>
<button onclick="document.getElementById('sub2').removeAttribute('disabled')"> add subject</button>
<input type="text" name="subject2" id="sub2" class="i2" size="20" disabled> <br>
<button onclick="document.getElementById('sub2').removeAttribute('disabled')"> add subject</button>