[tex] \sqrt[3]{54} = \sqrt[3]{2*3^3} =3 \sqrt[3]{2} [/tex]
[tex] \sqrt[3]{54} : \sqrt[3]{2} =3 \sqrt[3]{2} : \sqrt[3]{2} =3[/tex]
[tex](\sqrt{2})^2=2[/tex]
[tex]( \sqrt[4]{3} )^8=(3^{ \frac{1}{4} } )^8 =3^{ \frac{8}{4} }=3^2=9[/tex]
[tex]( \sqrt{2})^2 ( \sqrt[4]{3} )^8=2*9=18[/tex]