auto populate form with percentage calculation javascript

1function mult(value) {
2    var w, x, y, z;
3
4    x = 3;
5    y = (x / 100) * parseInt(value);
6    z = parseInt(value) + parseInt(y);
7
8
9    document.getElementById('percent').value = y;
10    document.getElementById('total').value = z;
11}