1:4 ÷ (1 - 5 ÷ 6)
2:4 ÷ (1 - (5 ÷ 6))
3:6 ÷ (5 ÷ 4 - 1)
4:6 ÷ ((5 ÷ 4) - 1)
或者6/(5/4-1)=24