2. Вычислите: а) 1/18 + (5/18 + 1/3); б) 4/15 + 7/24 + 5/24 + 1/15; в) 5/7 + 4/5 − 23/35.

1. а) \(\frac{1}{18}+\left(\frac{5}{18}+\frac{1}{3}\right)=\frac{1}{18}+\frac{5}{18}+\frac{6}{18}=\frac{12}{18}=\frac{2}{3}\).
2. б) \(\frac{4}{15}+\frac{7}{24}+\frac{5}{24}+\frac{1}{15}=\left(\frac{4}{15}+\frac{1}{15}\right)+\left(\frac{7}{24}+\frac{5}{24}\right)=\frac{5}{15}+\frac{12}{24}=\frac{1}{3}+\frac{1}{2}=\frac{5}{6}\).
3. в) \(\frac{5}{7}+\frac{4}{5}-\frac{23}{35}=\frac{25}{35}+\frac{28}{35}-\frac{23}{35}=\frac{30}{35}=\frac{6}{7}\).

Ответ: а) \(\frac{2}{3}\); б) \(\frac{5}{6}\); в) \(\frac{6}{7}\).