Ответ:

  1. \(\frac{12}{\sqrt6}=\frac{12\sqrt6}{6}=2\sqrt6\).
  2. \(\frac{1}{\sqrt{12}}=\frac{1}{2\sqrt3}=\frac{\sqrt3}{6}\).
  3. \(\frac{\sqrt5}{\sqrt{20}}=\sqrt{\frac{5}{20}}=\frac12\).
  4. \(\frac{8}{3\sqrt2}=\frac{8\sqrt2}{6}=\frac{4\sqrt2}{3}\).
  5. \(\frac{\sqrt6+1}{\sqrt6-1}=\frac{(\sqrt6+1)^2}{6-1}=\frac{7+2\sqrt6}{5}\).
  6. \(\frac{1}{2\sqrt3+3}=\frac{2\sqrt3-3}{(2\sqrt3)^2-3^2}=\frac{2\sqrt3-3}{3}\).