3целых 5/6 - 4целых 3/8 = ? 3целых 5/7 + m = 2целых 8/21

1) 3 целых 5/6 - 4 целых 3/8 = x
3 целых 20/24 - 4 целых 9/24 = x
- 1 целая 11/24 = x
2) 5/7 + m = 2 целых 8/21
15/21 + m = 2 целых 8/21
m = 2 целых 8/21 - 15/21
m = 1 целая 29/21 - 15/21
m = 1 целая 14/21
m = 1 целая 2/3