примеры на сложение дробей 1/7+2/21+3/7 д)7/10+2/15+11/30 в)1/15+2/45+7/15 е)1/12+1/8+1/12

1/7 + 2/21 + 3/7 = 3/21 + 2/21 + 9/21 = 14/21
7/10 + 2/15 + 11/30 = 21/30 + 4/30 + 11/30 = 36/30 = 1 6/30 = 1 1/5
1/15 + 2/45 + 7/15 = 3/45 + 2/45 + 21/45 = 26/45
1/12 + 1/8 + 1/12 = 2/24 + 3/24 + 2/24 = 7/24