Answer
$8m^{3}n^{6}$
Work Step by Step
$(64m^{6}n^{12})^{\frac{1}{2}}$
=$(8^{2}\times m^{6}\times n^{12})^{\frac{1}{2}}$
=$(8^{2})^{\frac{1}{2}}\times(m^{6})^{\frac{1}{2}}\times(n^{12})^{\frac{1}{2}}$
=$8\times m^{3}\times n^{6}$
=$8m^{3}n^{6}$