sergeev_bogdan

$(
  function() {
    function recalculateAll() {
      let res = parseInt($('#myselect_1').val()) 
              + parseInt($('#myselect_2').val());
      $('#outSumOption').text(res);
   
     if ($('#chk1').prop('checked')) {
        res *= 2;
      }
      $('#outSumChk1').text(res);

      if ($('#chk2').prop('checked')) {
        res += 100;
      }
      $('#outSumChk2').text(res);

      $('#outSum').text(res);
    }
  
    $('select, input[type="checkbox"]').change(
      function() {
        recalculateAll(); 
      }
    );
  
    recalculateAll();
  }
);