8 5/7 - (3,15 - 1 2/7) + 4,25 = 11,1
1) 3,15 - 1 2/7 = 3 3/20 - 1 2/7 = 3 21/140 - 1 40/140 = 2 161/140 - 1 40/140 = 1 целая 121/140
2) 8 5/7 - 1 121/140 = 8 100/140 - 1 121/140 = 7 240/140 - 1 121/140 = 6 119/140 = 6 целых 17/20 = 6,85
3) 6,85 + 4,25 = 11,1