7,9,12,12的24点答案：1:9 × 12 - 7 × 122:(9 × 12) - 7 × 123:9 × 12 -(7 × 12)4:(9 × 12) - (7 × 12)5:9 × 12 - 12 × 76:(9 × 12) - 12 × 77:9 × 12 -(12 × 7)8:(9 × 12) - (12 × 7)9:12 × 9 - 7...