I personally don't agree because change in GDP caused by decreased in fixed taxes should be
$\triangle$ fixed taxes $ \times \frac{-b}{1-MPE}$(fix tax multiplier), which turns out to be a positive number while change caused by decrease of Government Spending is
$\triangle$ Government Spending $ \times \frac{1}{1-MPE}$(autonomous multiplier) which is a negative number. Therefore I don't think we can make conclusion. Does anyone know what did I do wrong?