7. Вычислите (2 вариант)

a) \(\frac{3}{4} : \frac{16}{25} \cdot \frac{9}{5} = \frac{3}{4} \cdot \frac{25}{16} \cdot \frac{9}{5} = \frac{3 \cdot 25 \cdot 9}{4 \cdot 16 \cdot 5} = \frac{675}{320} = \frac{135}{64} = 2 \frac{7}{64}\) б) \((\frac{2}{5})^2 \cdot \frac{25}{16} - \frac{1}{8} = \frac{4}{25} \cdot \frac{25}{16} - \frac{1}{8} = \frac{4}{16} - \frac{1}{8} = \frac{1}{4} - \frac{1}{8} = \frac{2}{8} - \frac{1}{8} = \frac{1}{8}\)