乘号如果在分母
9-4.8/6*0.5
=9-6*0.8/6*0.5
=9-0.8*0.5
=8.6
乘号如果在分子
9-4.8/6*0.5
=9-4.8/3*2*0.5
=9-4.8/3
=9-1.6
=7.4