gonna_do
幼苗
共回答了15个问题采纳率:80% 举报
(+15)+(-20)+(+28)+(-10)+(-5)+(-7)
=15-20+28-10-5-7
=43-42
=1
2.(+2又3/4)+(-1又5/8)+(-5/6)+1/2
=3-(39/24+20/24)
=3-59/24
=13/24
3.(-3又1/2)+(-2又1/9)+3.5+(-8/9)+1/2
=[(-3又1/2)+1/2]-(2又1/9+8/9)+3.5
=-3-3+3.5
=-2.5
4.(-1)+(+2)+(-3)+(+4)+.+(-41)+(+42)
=1*21
=21
1年前
5