\(a,3\sqrt{27}-2\sqrt{75}+3\sqrt{12}-2\sqrt{147}\)
\(=9\sqrt{3}-10\sqrt{3}+6\sqrt{3}-14\sqrt{3}=-9\sqrt{3}\)
\(b,2\sqrt{2}+\sqrt{32}-\dfrac{1}{3}\sqrt{450}+\dfrac{2}{7}\sqrt{392}\)
\(=2\sqrt{2}+4\sqrt{2}-5\sqrt{2}+4\sqrt{2}=5\sqrt{2}\)
\(c,\sqrt{\left(2+7\right)^2}+\sqrt{\left(10-\sqrt{7}\right)^2}\)
\(=\sqrt{81}+\left|10-\sqrt{7}\right|=9+10-\sqrt{7}=19-\sqrt{7}\)