You can tell your instructor that I said he needs to pay attention to real world, good coding practices. Example:

Code:
  decFractionOneNumerator = Convert.ToDecimal(Me.txtFractionOneNumerator.Text)
  decFractionOneDenominator = Convert.ToDecimal(Me.txtFractionOneDenominator.Text)
  decFrationTwoNumerator = Convert.ToDecimal(Me.txtFractionTwoNumerator.Text)
  decFractionTwoDenominator = Convert.ToDecimal(Me.txtFractionTwoDenominator.Text)
What if the user entered something other than numbers into the text fields? Ask him that?