5/6减1/6加1/2
=2/3+1/2
=7/6
1减2/7减3/7
=1-5/7
=2/7
2减5/12减11/36
=72/36-15/36-11/36
=46/36
=23/18
1/8加1/4加5/6
=3/24+6/24+20/24
=29/24
如果本题有什么不明白可以追问,