5.543 Найдите значение выражения: а) (5/6 + 4/9) - 5/6 * 4/9; б) 2/8 * 8/8 + (3 1/3 - 2 3/5) : 7/15

а) \((\frac{5}{6} + \frac{4}{9}) - \frac{5}{6} \cdot \frac{4}{9}\) = \((\frac{15}{18} + \frac{8}{18}) - \frac{20}{54}\) = \(\frac{23}{18} - \frac{20}{54}\) = \(\frac{69}{54} - \frac{20}{54}\) = \(\frac{49}{54}\) б) \(\frac{2}{8} \cdot \frac{8}{8} + (3 \frac{1}{3} - 2 \frac{3}{5}) : \frac{7}{15}\) = \(\frac{16}{64} + (\frac{10}{3} - \frac{13}{5}) : \frac{7}{15}\) = \(\frac{1}{4} + (\frac{50}{15} - \frac{39}{15}) : \frac{7}{15}\) = \(\frac{1}{4} + \frac{11}{15} : \frac{7}{15}\) = \(\frac{1}{4} + \frac{11}{15} \cdot \frac{15}{7}\) = \(\frac{1}{4} + \frac{11}{7}\) = \(\frac{7}{28} + \frac{44}{28}\) = \(\frac{51}{28}\)