5/6+1/宽陆4-2/3
=10/12+3/扮锋12-8/12
=5/12
3/5+7/10-11/20
=12/20+14/20-11/20
=15/20
=3/4
7/8-5/12+1/6
=21/24-10/24+4/24
=15/24
=5/8
7/15+2/7+8/15
=(7/15+8/15)+2/7
=1+2/7
=1又2/7
9/10-(1/6+3/5)
=9/10-1/慎缺顷6-3/5
=27/30-5/30-18/30
=4/30
=2/15
5/12-(1/3-1/4)
=5/12-1/3+1/4
=5/12-4/12+3/12
=4/12
=1/3