\(\dfrac{2}{\sqrt{3}-1}-\dfrac{1}{\sqrt{3}-2}+\dfrac{12}{\sqrt{3}+3}=\dfrac{2\left(\sqrt{3}+1\right)}{2}-\dfrac{\sqrt{3}+2}{-1}+\dfrac{12\left(\sqrt{3}-3\right)}{-6}=\sqrt{3}+1+\sqrt{3}+2-2\sqrt{3}+6=9\)
\(\dfrac{2}{\sqrt{3}-1}+\dfrac{1}{2-\sqrt{3}}+\dfrac{12}{3+\sqrt{3}}\)
\(=\sqrt{3}+1+2+\sqrt{3}+6-2\sqrt{3}\)
=9