5/6+1/12-2/3
=10/12+1/12-8/12
=3/12
=1/4
10/9-(8/9+1/6)
=10/9-8/9-1/6
=2/9-1/6
=4/18-3/18
=1/18问错了，第一题是4/5-1/2+3/44/5-1/2+3/4 =0.8-0.5+0.75 =0.3+0.75 =1.05