12. Вычислите: 1) 5 7/18 − 3/4; 2) 5 4/15 − 2 5/20; 3) 2 6/12 + 3 9/16; 4) 12 6/9 − 7 4/15.

1. \(5\frac{7}{18}-\frac{3}{4}=5+\frac{14}{36}-\frac{27}{36}=4\frac{23}{36}\).
2. \(5\frac{4}{15}-2\frac{5}{20}=5\frac{4}{15}-2\frac{1}{4}=3+\frac{16}{60}-\frac{15}{60}=3\frac{1}{60}\).
3. \(2\frac{6}{12}+3\frac{9}{16}=2\frac{1}{2}+3\frac{9}{16}=6\frac{1}{16}\).
4. \(12\frac{6}{9}-7\frac{4}{15}=12\frac{2}{3}-7\frac{4}{15}=5+\frac{10}{15}-\frac{4}{15}=5\frac{2}{5}\).

Ответ: 1) \(4\frac{23}{36}\); 2) \(3\frac{1}{60}\); 3) \(6\frac{1}{16}\); 4) \(5\frac{2}{5}\).