ДАМ 20 поинтов посчитайте ​

2/7 + 5/8 + 1/2 = 16/56 + 35/56 + 28/56= 79/56 = 1 23/56

1/2 - 2/15 + 3/5 = 15/30 - 4/30 + 18/30 = 29/30

6/7 - 1/6 + 2/9 = 108/126 - 21/126 + 28/126= 115/126