5,5,5,1的24点答案：
1:5 × (5 - 1 ÷ 5) =24
2:5 × (5 - (1 ÷ 5))=24
3:(5 - 1 ÷ 5) × 5=24
4:(5 - (1 ÷ 5)) × 5=24