2/3+1/4-5/12
=8/12+3/12-5/12
=6/12
=1/2
7/8-5/6+2/3
=21/24-20/24+16/24
=17/24
7/10-(1-3/5)
=7/10-2/5
=3/10
5/12+(2/3-1/2)
=5/12+1/6
=7/12
4/5+3/10-1/2
=8/10+3/10-5/10
=6/10
=3/5
1/2-(1/5+1/4)
=1/2-9/20
=10/20-9/20
=1/20
在右上角点击【评价】,然后就可以选择【满意,问题已经完美解决】了.