7 8 9 2算24点

1: (7 + 9) × 2 - 8
2: ((7 + 9) × 2) - 8
3: (9 + 7) × 2 - 8
4: ((9 + 7) × 2) - 8
5: (2 × (7 + 9)) - 8
6: 2 × (7 + 9) - 8
7: (2 × (9 + 7)) - 8
8: 2 × (9 + 7) - 8