a) \(3\sqrt{18}-2\sqrt{50}-\sqrt{6-4\sqrt{2}}\)
\(=9\sqrt{2}-10\sqrt{2}-\left(2-\sqrt{2}\right)\)
\(=-\sqrt{2}-2+\sqrt{2}\)
\(=-2\)
b) \(3\sqrt{\frac{2}{3}}+\frac{2}{\sqrt{6}-2}-\frac{12}{\sqrt{6}}\)
\(=3\sqrt{\frac{2.3}{3.3}}+\frac{2.\left(\sqrt{6}+2\right)}{\left(\sqrt{6}\right)^2-2^2}-\frac{12\sqrt{6}}{6}\)
\(=\sqrt{6}+\sqrt{6}+2-2\sqrt{6}\)
\(=2\)