6÷(5÷4-1)=244÷(1-5÷6)=24
1: 4 ÷ (1 - 5 ÷ 6)2: 4 ÷ (1 - (5 ÷ 6))3: 6 ÷ (5 ÷ 4 - 1)4: 6 ÷ ((5 ÷ 4) - 1)