JSFiddle - React, Tailwind, and code Playground

HTML

<div class="equation">
    <input class="common"  value="0" />
    <input class="common"  value="0" />
    <input name="3" value="0" readonly="readonly" />
</div>

JavaScript

$('.equation').each(function(index, element){
    element = $(element);
    element.find('.common').change(function () {
        var val1 = parseFloat(element.find('input[name="1"]').val());
        var val2 = parseFloat(element.find('input[name="2"]').val());
        element.find('input[name="3"]').val(val1 + val2);
    });
});