2又20分之3+1.09一2又5分之4+2分之1
=2+3/20+1.09-2-4/5+1/2
=0.15+1.09-0.8+0.5
=1.29-0.8
=0.49;
1又5分之1一［3分之2+0.2一（0.8一15分之2）］
=1+1/5-(2/3+0.2-0.8+2/15)
=6/5-2/3-0.2+0.8-2/15
=6/15+0.6
=2/5+3/5
=1;
如果本题有什么不明白可以追问,还有一题了写好了