Решите задачу 321, найдите значение выражений.

a) \( \frac{1}{2} + \frac{5}{8} = \frac{4}{8} + \frac{5}{8} = \frac{9}{8} \). b) \( \frac{3}{4} - \frac{1}{2} = \frac{6}{8} - \frac{4}{8} = \frac{2}{8} = \frac{1}{4} \). c) \( \frac{7}{10} - \frac{3}{5} = \frac{7}{10} - \frac{6}{10} = \frac{1}{10} \). d) \( \frac{5}{9} - \frac{5}{12} = \frac{20}{36} - \frac{15}{36} = \frac{5}{36} \). e) \( \frac{7}{12} - \frac{7}{20} = \frac{140}{240} - \frac{84}{240} = \frac{56}{240} = \frac{7}{30} \).