[tex]a = \Big(\sqrt{27}+2\sqrt{12}-\dfrac{6}{\sqrt3}\Big)\cdot \dfrac{5}{\sqrt3} \\ \\ a = \Big(\sqrt{3}\cdot \sqrt9+2\cdot \sqrt3\cdot \sqrt4-\dfrac{6}{\sqrt3}\Big)\cdot \dfrac{5}{\sqrt3} \\ \\ a = \sqrt9\cdot 5+2\sqrt4\cdot 5-\dfrac{6\cdot 5}{3} \\ \\ a = 3\cdot 5+2\cdot 2\cdot 5-2\cdot 5 \\ \\ a = 15+20-10 \\ \\ \boxed{a = 25}[/tex]
[tex]b=(0,25)^{-1} \\ \\ b = \Big(\dfrac{1}{4}\Big)^{-1} \\ \\\boxed{ b = 4}[/tex]
