JSFiddle - React, Tailwind, and code Playground
HTML
<div id="price11">Price 1 <label><input id="price1" type="text"></label></div> <div id="price21">Price 2 <label><input id="price2" type="text"></label></div> <div id="rate1">Rate <label><input id="rate" type="text"></label></div>
<a href="#" id="calc">calc</a>
JavaScript
$("#calc").click(function() {
var result = (parseInt(($("#price1").val()) * 100) / parseInt($("#price2").val()));
if (!isFinite(result)) result = 0;
console.log(result);
$("#rate").val(result);
});