12,9,9,4怎末运算才能得24

题目

12,9,9,4怎末运算才能得24
一个数只能用一次得-24也行

答案

1: 4 × (9 + 9 - 12)
2: 4 × ((9 + 9) - 12)
3: 4 × (9 + (9 - 12))
4: 4 × (9 - 12 + 9)
5: 4 × ((9 - 12) + 9)
6: 4 × (9 - (12 - 9))
7: (4 - 12 ÷ 9) × 9
8: (4 - (12 ÷ 9)) × 9
9: 9 × (4 - 12 ÷ 9)
10: 9 × (4 - (12 ÷ 9))
11: (9 + 9 - 12) × 4
12: ((9 + 9) - 12) × 4
13: (9 + (9 - 12)) × 4
14: (9 - 12 + 9) × 4
15: ((9 - 12) + 9) × 4
16: (9 - (12 - 9)) × 4