private void MultiTextBox_KeyUp(object sender, KeyEventArgs e)
        {
            string strValue = MultiTextBox.Text.Trim().ToString();

            multi = input.ReadIntegerValue(strValue);
            if (multi < -0.1)
            {
                Reset();
            }
            if (strValue.Length > 3)
            {
                MessageBox.Show("Max 100%");
                MultiTextBox.Clear();
            }
            SetPercent();
        }
 //Reset values
 private void Reset()
 {
     subtractionTextBox.Clear();
     MultiTextBox.Clear();
     additionTextBox.Clear();
     answerTextBox.Clear();
     MultiRatioTextbox.Clear();
     AddSubRatio.Clear();
     add                  = 0;
     subtract             = 0;
     multi                = 0;
     sum                  = 0;
     labelMaxPercent.Text = "0%";
     labelQuestion.Text   = "";
     count                = 0;
     rightTestAnswer      = 0;
 }