JSFiddle - React, Tailwind, and code Playground

HTML

<input type="button" value="Start" onclick="newProblem()">
<p class="number first-number" id="firstNumberDiv"></p>
    <p class="number first-number" id="secondNumberDiv"></p>

JavaScript

function createProblem(){
var x=Math.floor(Math.random() * 10);
var y=Math.floor(Math.random() * 10);    
$("#firstNumberDiv").text(x);
$("#secondNumberDiv").text(y);

}
newProblem(){    
$(document).ready(createProblem());
}