除法那部分先提取公因式 (8.1-5.4)÷3.6 = (0.9 x 9 - 0.9 x 6)÷ (0.9 x 4)= 0.9 x (9 - 6) ÷ (0.9 x 4)= 0.9 x (9 - 6) ÷ 0.9 ÷ 4= (9 - 6) ÷ 4= 0.75 (8.1-5.4)÷3.6+85.7= 0.75 + 85.7= 85 + 0.7 + 0.75= 85 + (0.7 + 0.75)= 85 + 1.45= 86.45