1)30 ÷ 27 = 30/1 × 1/27 = 30/27= 10/9 = 1 1/9
2)1 1/9 - 1/3 = 10/9 - 1/3 = (10 × 1 - 1 × 3)/9 = 10/9 - 3/9 = 7/9
3)7/9 × 2 1/7 = 7/9 × 15/7 = 105/63= 5/3 = 1 2/3
4)1 2/3 + 2/5 = 5/3 + 2/5 =(5 × 5 + 2 × 3)/15 = 25/15 + 6/15 = 31/15 = 2 1/15
только ответ в этом примере 2 1/15, а не 2 2/9