311.
1) (12 19/24 + 5 19/28) - 3 19/24 = (12 19/24 - 3 19/24) + 5 19/28 = 9 + 5 19/28 = 14 19/28.
2) 6 4/9 - (1 7/24 + 4 4/9) = 6 4/9 - 4 4/9 - 1 7/24 = 2 - 1 7/24 = 1 24/24 - 1 7/24 = 17/24.
