Đáp án:
$\begin{array}{l}
a)\sqrt {\dfrac{{{{12}^5}}}{{{3^3}{{.4}^3}}}} = \sqrt {\dfrac{{{{\left( {4.3} \right)}^5}}}{{{3^3}{{.4}^3}}}} = \sqrt {{3^2}{{.4}^2}} = 3.4 = 12\\
b)\dfrac{{\sqrt {180} }}{{\sqrt 5 }}:\dfrac{{\sqrt {200} }}{{\sqrt 8 }}\\
= \sqrt {\dfrac{{180}}{5}} :\sqrt {\dfrac{{200}}{8}} \\
= \sqrt {36} :\sqrt {25} \\
= 6:5\\
= \dfrac{6}{5}
\end{array}$