в) \((z + \frac{5}{12}) - \frac{9}{20} = \frac{11}{15}\)

\(z + \frac{5}{12} = \frac{11}{15} + \frac{9}{20}\)

Приведём дроби к знаменателю 60:

\(z + \frac{5}{12} = \frac{44}{60} + \frac{27}{60} = \frac{71}{60}\)

\(z = \frac{71}{60} - \frac{5}{12} = \frac{71}{60} - \frac{25}{60} = \frac{46}{60} = \frac{23}{30}\)

Проверка: \(\left(\frac{23}{30} + \frac{5}{12}\right) - \frac{9}{20} = \frac{11}{15}\).

Ответ: \(z = \frac{23}{30}\).