2. Вычислите: а) 5/7 * (21/20 - 7/30) + 16/21 : 8/7; б) (1 1/2)^3 : (1 - 1/3 * 1 1/4)^2

а) \( \frac{5}{7} \cdot (\frac{21}{20} - \frac{7}{30}) + \frac{16}{21} : \frac{8}{7} = \frac{5}{7} \cdot (\frac{63 - 14}{60}) + \frac{16}{21} \cdot \frac{7}{8} = \frac{5}{7} \cdot \frac{49}{60} + \frac{2}{3} = \frac{5 \cdot 49}{7 \cdot 60} + \frac{2}{3} = \frac{245}{420} + \frac{2}{3} = \frac{7}{12} + \frac{2}{3} = \frac{7 + 8}{12} = \frac{15}{12} = \frac{5}{4} = 1 \frac{1}{4} \) б) \( (1 \frac{1}{2})^3 : (1 - \frac{1}{3} \cdot 1 \frac{1}{4})^2 = (\frac{3}{2})^3 : (1 - \frac{1}{3} \cdot \frac{5}{4})^2 = \frac{27}{8} : (1 - \frac{5}{12})^2 = \frac{27}{8} : (\frac{12 - 5}{12})^2 = \frac{27}{8} : (\frac{7}{12})^2 = \frac{27}{8} : \frac{49}{144} = \frac{27}{8} \cdot \frac{144}{49} = \frac{27 \cdot 144}{8 \cdot 49} = \frac{27 \cdot 18}{49} = \frac{486}{49} = 9 \frac{45}{49} \) Ответ: а) 1 1/4 б) 9 45/49