\[\boxed{\text{5.464.}}\]
\[\textbf{а)}\ \ \left( \frac{4}{5} \right)^{2} = \frac{4}{5} \cdot \frac{4}{5} = \frac{16}{25}\]
\[\textbf{б)}\ \left( \frac{11}{15} \right)^{2} = \frac{11}{15} \cdot \frac{11}{15} = \frac{121}{225}\]
\[\textbf{в)}\ \left( \frac{7}{6} \right)^{3} = \frac{7}{6} \cdot \frac{7}{6} \cdot \frac{7}{6} = \frac{343}{216}\]
\[\textbf{г)}\ \left( \frac{3}{7} \right)^{3} = \frac{3}{7} \cdot \frac{3}{7} \cdot \frac{3}{7} = \frac{27}{343}\]
\[\textbf{д)}\ \left( \frac{1}{4} \right)^{3} = \frac{1}{4} \cdot \frac{1}{4} \cdot \frac{1}{4} = \frac{1}{64}\]