280. Выполните вычитание: 1) 3 1/12 − 1/6; 2) 8 7/30 − 2 9/20; 3) 7 10/51 − 4 21/34; 4) 5 1/4 − 1 3/8.

1. \(3\frac{1}{12}-\frac{1}{6}=3\frac{1}{12}-\frac{2}{12}=2\frac{11}{12}\).
2. \(8\frac{7}{30}-2\frac{9}{20}=8\frac{14}{60}-2\frac{27}{60}=5\frac{47}{60}\).
3. \(7\frac{10}{51}-4\frac{21}{34}=7\frac{20}{102}-4\frac{63}{102}=2\frac{59}{102}\).
4. \(5\frac{1}{4}-1\frac{3}{8}=5\frac{2}{8}-1\frac{3}{8}=3\frac{7}{8}\).

Ответ: 1) \(2\frac{11}{12}\); 2) \(5\frac{47}{60}\); 3) \(2\frac{59}{102}\); 4) \(3\frac{7}{8}\).