1.8乘百分之40加上五分之二除于二分之一2.4点15减3点75乘百分之10减八分之五.[急.]

1.8*40%+2/5 /1/2
=8*04+2/5*2
=3.2+0.8
=4
2.4.15-3.75*10%-5/8
=4.15-0.375-0.625
=4.15-(0.375+0.625)
=4.15-1
=3.15
3.1-39%*1/2 /0.195
=1-0.39*0.5/0.195
=1-0.195/0.195
=1-1
=0