a)
[tex]\it(5\sqrt6)\cdot(2\sqrt{15}):(15\sqrt5)=\dfrac{10\sqrt{90}}{15\sqrt5}=\dfrac{\ 10^{(5}}{15}\cdot\sqrt{\dfrac{90}{5}}=\dfrac{2}{3}\cdot\sqrt{18}=\dfrac{2}{3}\cdot\sqrt{9\cdot2}=\\ \\ \\ =\dfrac{2}{3}\cdot3\sqrt2=2\sqrt2[/tex]
e)
[tex]\it (2\sqrt3)^3:(\sqrt2)^4=\dfrac{2\sqrt3\cdot2\sqrt3\cdot2\sqrt3}{\sqrt2\cdot\sqrt2\cdot\sqrt2\cdot\sqrt2}=\dfrac{8\cdot3\sqrt3}{4}=2\cdot3\sqrt3=6\sqrt3[/tex]
b)
[tex](3\sqrt{12})\cdot(-\sqrt8):(6\sqrt6)=-(3\sqrt{96}):(6\sqrt6)=-\dfrac{3\sqrt{96}}{6\sqrt6}=-\dfrac{\sqrt{16}}{2}=-\dfrac{4}{2}=-2[/tex]
