(8.27+1.73)-(1.35+4.65)=10.0-6.04.0
(8.27+1.73)-(1.35+4.65)=10-6=4
(8.27+1.73)-(1.35+4.65) =4
8.27+1.73 -1.35-4.65 最后他俩结果相加
8.27+1.73先,之后-(1.35+4.65)