279. Вычислите: 1) 1 − 13/55; 2) 6 − 9/20; 3) 10 − 5 12/35; 4) 8 − 4 5/22.

1. \(1-\frac{13}{55}=\frac{55-13}{55}=\frac{42}{55}\).
2. \(6-\frac{9}{20}=5\frac{20-9}{20}=5\frac{11}{20}\).
3. \(10-5\frac{12}{35}=4\frac{35-12}{35}=4\frac{23}{35}\).
4. \(8-4\frac{5}{22}=3\frac{22-5}{22}=3\frac{17}{22}\).

Ответ: 1) \(\frac{42}{55}\); 2) \(5\frac{11}{20}\); 3) \(4\frac{23}{35}\); 4) \(3\frac{17}{22}\).