JSFiddle - React, Tailwind, and code Playground

HTML

<input type="checkbox" name="Pacote" value="primeira opcao" onclick="pega(event)">
<input type="text" id="number1" value ="1"/>

<input type="checkbox" name="Pacote" value="segunda opcao" onclick="pega(event)">
<input type="text" id="number2" value="10" />
<div id="total"></div>

JavaScript

var opcoes = document.querySelectorAll('input[type="checkbox"]');
var inputs = document.querySelectorAll('input[type="text"]');

function lerValores(els) {
  return [].map.call(els, function (el) {
    return el.checked;
  });

}

function pega(e) {
  var total = 0;
  lerValores(opcoes).forEach(function (checked, i) {
    if (checked) total += parseInt(inputs[i].value, 10);;
  });
  document.getElementById("total").innerHTML = total;
}