JSFiddle - React, Tailwind, and code Playground

HTML

<span class="cena-vebsajt">6000</span>
<span class="cena-hosting">1200</span>
<span class="result"></span>

JavaScript

var one=parseFloat($('.cena-vebsajt').text());
var two=parseFloat($('.cena-hosting').text());
var res=one+two;

$('.result').text(res);