\[\begin{array}{l}
\frac{{\sqrt 8 - \sqrt {12} }}{{\sqrt {18} - \sqrt {48} }} - \frac{{\sqrt 5 + \sqrt {27} }}{{\sqrt {30} + \sqrt {162} }}\\
= \frac{{\left( {\sqrt 8 - \sqrt {12} } \right)\left( {\sqrt {18} + \sqrt {48} } \right)}}{{\left( {\sqrt {18} - \sqrt {48} } \right)\left( {\sqrt {18} + \sqrt {48} } \right)}} - \frac{{\left( {\sqrt 5 + \sqrt {27} } \right)\left( {\sqrt {30} - \sqrt {162} } \right)}}{{\left( {\sqrt {30} + \sqrt {162} } \right)\left( {\sqrt {30} - \sqrt {162} } \right)}}\\
= \frac{{\sqrt {144} + \sqrt {384} - \sqrt {216} - \sqrt {576} }}{{18 - 48}} - \frac{{\sqrt {150} - \sqrt {810} + \sqrt {810} - \sqrt {4374} }}{{30 - 162}}\\
= \frac{{12 + 8\sqrt 6 - 6\sqrt 6 - 24}}{{ - 30}} - \frac{{5\sqrt 6 - 27\sqrt 6 }}{{ - 132}}\\
= \frac{{2\sqrt 6 - 12}}{{ - 30}} + \frac{{ - 22\sqrt 6 }}{{132}}\\
= \frac{{12 - 7\sqrt 6 }}{{30}}
\end{array}\]