a) \(\frac{4}{5} + \frac{2}{3} = \frac{4 \cdot 3 + 2 \cdot 5}{15} = \frac{12 + 10}{15} = \frac{22}{15} = 1 \frac{7}{15}\)
б) \(\frac{5}{6} + \frac{7}{9} = \frac{5 \cdot 3 + 7 \cdot 2}{18} = \frac{15 + 14}{18} = \frac{29}{18} = 1 \frac{11}{18}\)
в) \(\frac{3}{4} - \frac{1}{6} = \frac{3 \cdot 3 - 1 \cdot 2}{12} = \frac{9 - 2}{12} = \frac{7}{12}\)
г) \(\frac{7}{8} - \frac{5}{6} = \frac{7 \cdot 3 - 5 \cdot 4}{24} = \frac{21 - 20}{24} = \frac{1}{24}\)
Ответ: a) \(1 \frac{7}{15}\); б) \(1 \frac{11}{18}\); в) \(\frac{7}{12}\); г) \(\frac{1}{24}\).