$${\left({\mathtt{6}}{\mathtt{\,\times\,}}{{\mathtt{cd}}}^{-{\mathtt{1}}}\right)}^{-{\mathtt{3}}}$$
$$\\(6\times cd^{-1})^{-3}\\\\ =(\frac{6\times cd^{-1}}{1})^{-3}\\\\ =(\frac{6\times c}{d})^{-3}\\\\ =(\frac{d}{6\times c})^{+3}\\\\ =\frac{d^3}{216\;c^3}\\\\$$
