need help

$\sqrt{27} - \sqrt{12}*\sqrt{300} + \sqrt{24}*\sqrt{81}\\ =\sqrt{9*3} - \sqrt{4*3}*\sqrt{100*3} + \sqrt{4*6}*9\\ =3\sqrt{3} - 2\sqrt{3}*10\sqrt{3} + 2\sqrt{6}*9\\ =3\sqrt{3} - 20\sqrt{9}+ 18\sqrt{6}\\ =3\sqrt{3} - 20*3+ 18\sqrt{6}\\ =3\sqrt{3} - 60+ 18\sqrt{6}\\$