5.543 Найдите значение выражения: a) \((\frac{5}{6} + \frac{4}{9}) - \frac{5}{6} \div \frac{4}{9}\); б) \(\frac{2}{8} \div \frac{8}{8} + (3\frac{1}{3} - 2\frac{3}{5}) \div \frac{7}{15}\)?

a) \((\frac{5}{6} + \frac{4}{9}) - \frac{5}{6} \div \frac{4}{9} = (\frac{15}{18} + \frac{8}{18}) - \frac{5}{6} \cdot \frac{9}{4} = \frac{23}{18} - \frac{45}{24} = \frac{23}{18} - \frac{15}{8} = \frac{92}{72} - \frac{135}{72} = -\frac{43}{72}\) б) \(\frac{2}{8} \div \frac{8}{8} + (3\frac{1}{3} - 2\frac{3}{5}) \div \frac{7}{15} = \frac{2}{8} \div 1 + (\frac{10}{3} - \frac{13}{5}) \div \frac{7}{15} = \frac{1}{4} + (\frac{50}{15} - \frac{39}{15}) \div \frac{7}{15} = \frac{1}{4} + \frac{11}{15} \div \frac{7}{15} = \frac{1}{4} + \frac{11}{15} \cdot \frac{15}{7} = \frac{1}{4} + \frac{11}{7} = \frac{7}{28} + \frac{44}{28} = \frac{51}{28} = 1\frac{23}{28}\)