112÷()=()......7有几种填法

28种 1: 4 × (5 - 6 + 7) 2: 4 × ((5 - 6) + 7) 3: 4 × (5 - (6 - 7)) 4: 4 × (5 + 7 - 6) 5: 4 × ((5 + 7) - 6) 6: 4 × (5 + (7 - 6)) 7: 4 × (7 + 5 - 6) 8: 4 × ((7 + 5) - 6) 9: 4 × (7 + (5 - 6)) 10: 4 × (7 - 6 + 5) 11: 4 × ((7 - 6) + 5) 12: 4 × (7 - (6 - 5)) 13: (5 - 6 + 7) × 4 14: ((5 - 6) + 7) × 4 15: (5 - (6 - 7)) × 4 16: (5 + 7 - 6) × 4 17: ((5 + 7) - 6) × 4 18: (5 + (7 - 6)) × 4 19: (5 + 7) × (6 - 4) 20: (6 - 4) × (5 + 7) 21: (6 - 4) × (7 + 5) 22: (7 + 5 - 6) × 4 23: ((7 + 5) - 6) × 4 24: (7 + (5 - 6)) × 4 25: (7 + 5) × (6 - 4) 26: (7 - 6 + 5) × 4 27: ((7 - 6) + 5) × 4 28: (7 - (6 - 5)) × 4