Вычислите: а) (4/5 − 2/7) − 3/70; б) 7/9 + 1/15 − 5/18 + 1/30; в) 11/12 − 1/18.

1. \(\left(\frac{4}{5}-\frac{2}{7}\right)-\frac{3}{70}=\left(\frac{28}{35}-\frac{10}{35}\right)-\frac{3}{70}=\frac{18}{35}-\frac{3}{70}=\frac{36}{70}-\frac{3}{70}=\frac{33}{70}\).
2. \(\frac{7}{9}+\frac{1}{15}-\frac{5}{18}+\frac{1}{30}=\frac{70}{90}+\frac{6}{90}-\frac{25}{90}+\frac{3}{90}=\frac{54}{90}=\frac{3}{5}\).
3. \(\frac{11}{12}-\frac{1}{18}=\frac{33}{36}-\frac{2}{36}=\frac{31}{36}\).

Ответ: а) \(\frac{33}{70}\); б) \(\frac{3}{5}\); в) \(\frac{31}{36}\).