解?$：(1)$?原式?$=27 \sqrt {5} \div \frac {3 \sqrt {5}}{5} ×\frac {3}{2} \sqrt {\frac {8}{3}} $?
?$=27 \sqrt {5} \div \frac {3 \sqrt {5}}{5} ×\sqrt {6} $?
?$=45 \sqrt {6}$?
?$(2)$?原式?$=(\sqrt {5})^2-2 ×\sqrt {5} ×\sqrt {3}+(\sqrt {3})^2 $?
?$=5-2 \sqrt {15}+3 $?
?$=8-2 \sqrt {15}$?
