1:(10 × 10 - 4) ÷ 4
2:((10 × 10) - 4) ÷ 4
1:(1 - 7) × (3 - 7)
2:(3 - 7) × (1 - 7)
3:(7 - 1) × (7 - 3)
4:(7 - 3) × (7 - 1)