Пошаговое объяснение:
1) 3. 1/4 + 2. 1/6 =
3. 3/12 + 2. 2/12 = 5. 5/12
2) 5. 5/12 : 2. 3/5 =
65/12 : 13/5 = 65/12 * 5/13 = 5/12 * 5/1 = 25/12 = 2. 1/12
3) 2. 1/12 + 1. 1/6 =
2. 1/12 + 1. 2/12 =
3. 3/12 = 3. 1/4
