问题描述：
2 7 5 4 ,7 7 5 1 ,7 9 2 5 算24点
问题解答：
我来补答
1.{7+5}/2*4 1:7 × 5 -(9 + 2) 2:(7 × 5) - (9 + 2) 3:7 × 5 - 9 - 2 4:(7 × 5) - 9 - 2 5:(7 × 5 - 9) - 2 6:((7 × 5) - 9) - 2 7:7 × 5 -(2 + 9) 8:(7 × 5) - (2 + 9) 9:7 × 5 - 2 - 9 10:(7 × 5) - 2 - 9 11:(7 × 5 - 2) - 9 12:((7 × 5) - 2) - 9 13:5 × 7 -(9 + 2) 14:(5 × 7) - (9 + 2) 15:5 × 7 - 9 - 2 16:(5 × 7) - 9 - 2 17:(5 × 7 - 9) - 2 18:((5 × 7) - 9) - 2 19:5 × 7 -(2 + 9) 20:(5 × 7) - (2 + 9) 21:5 × 7 - 2 - 9 22:(5 × 7) - 2 - 9 23:(5 × 7 - 2) - 9 24:((5 × 7) - 2) - 9
