calculating salary

'hi i'm having problem with calcolating the total it gives me zero ' can any one help me with that Private Sub Button12_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button12.Click Dim advanced As Double Dim benefit As Double Dim basic As Double Dim hra As Double Dim med_all As Double Dim child As Double Dim hma As Double Dim total As Double advanced = Convert.ToDouble(TextBox6.Text) benefit = Convert.ToDouble(TextBox7.Text) basic = Convert.ToDouble(TextBox8.Text) hra = Convert.ToDouble(TextBox9.Text) med_all = Convert.ToDouble(TextBox10.Text) child = Convert.ToDouble(TextBox11.Text) hma = Convert.ToDouble(TextBox12.Text) total = Convert.ToDouble(TextBox13.Text) TextBox6.Text = advanced.ToString TextBox7.Text = benefit.ToString TextBox8.Text = basic.ToString TextBox9.Text = hra.ToString TextBox10.Text = med_all.ToString TextBox11.Text = child.ToString TextBox12.Text = hma.ToString TextBox13.Text = total.ToString hra = hra * 5 / 100 * 100 med_all = med_all * 5 / 100 * 100 child = child * 5 / 100 * 100 hma = hma * 8 / 100 * 100 total = basic + advanced + benefit + hra + med_all + child + hma End Sub