Sqrt(20) * (Sqrt(10) + Sqrt(5) - 5(Sqrt(8)) = Sqrt(4*5) * (Sqrt(2 * 5) + Sqrt(5) - 5*Sqrt(2 * 4)) = 2Sqrt(5) * (Sqrt(2) * Sqrt(5)+Sqrt(5) - 10Sqrt(2)) = 2Sqrt(5) * Sqrt(2) * Sqrt(5) + 2Sqrt(5)*Sqrt(5) - 2Sqrt(5) * 10Sqrt(2)) = 2*5*Sqrt(2) + 2*5 -
20*Sqrt(2)*Sqrt(5) = 10Sqrt(2) + 10 - 20Sqrt(2)*Sqrt(5) = 10(Sqrt(2) + 1 - 2 * Sqrt(10))