function calculate() {
  var table = document.getElementById("myTable");
  var rows = table.rows;
     for (var i = 1; i < rows.length; i++) {
         var cells = rows[i].cells;
         var sum = 0;


         for (var x = 2; x < cells.length-1; x++) {
              var cell = cells[x];
              sum += parseInt(cell.innerHTML);

         }
    var average = Math.round(sum / 5);
    rows[i].cells[7].innerHTML = average + '%';
    }
}