$\left. \begin{matrix}{{I}_{3}}={{I}_{6}}+{{I}_{12}}  \\{{I}_{6}}\times 6={{I}_{12}}\times 12\Rightarrow {{I}_{6}}=2{{I}_{12}}  \\\end{matrix} \right\}\Rightarrow {{I}_{3}}=\frac{3}{2}{{I}_{6}}\Rightarrow {{I}_{6}}=\frac{2}{3}{{I}_{3}}$ $\frac{{{p}_{6}}}{{{p}_{3}}}=\frac{R{{I}^{2}}_{6}}{R{{I}^{2}}_{3}}=\frac{6\times \left( \frac{2}{3}{{I}_{3}} \right)}{3\times {{I}^{2}}_{3}}=\frac{8}{5}$