a)

$3\sqrt{12}+3\sqrt{50}-5\sqrt{32}+2\sqrt{75}=3\sqrt{4\cdot 3}+3\sqrt{25\cdot 2}-5\sqrt{16\cdot 2}+2\sqrt{3\cdot 25}=$

$=3\cdot 2\sqrt{3}+3\cdot 5\sqrt{2}-5\cdot 4\sqrt{2}+2\cdot 5\sqrt{3}=$   $6\sqrt{3}+15\sqrt{2}-20\sqrt{2}+10\sqrt{3}=\underline{\underline{16\sqrt{3}-5\sqrt{2}}}$