\[\frac{12^{6}}{3^{5} \cdot 4^{5}} = \frac{3^{6} \cdot 4^{6}}{3^{5} \cdot 4^{5}} = 3^{6 - 5} \cdot 4^{6 - 5} =\]
\[= 3 \cdot 4 = 12.\]