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

1. \(\frac47+\frac25=\frac{20}{35}+\frac{14}{35}=\frac{34}{35}\).
2. \(\frac7{12}-\frac59=\frac{21}{36}-\frac{20}{36}=\frac1{36}\).
3. \(2\frac34+3\frac25=5+\frac34+\frac25=5+\frac{15}{20}+\frac8{20}=6\frac3{20}\).
4. \(3\frac49-2\frac16=1+\frac49-\frac16=1+\frac8{18}-\frac3{18}=1\frac5{18}\).

Ответ: 1) \(\frac{34}{35}\); 2) \(\frac1{36}\); 3) \(6\frac3{20}\); 4) \(1\frac5{18}\).