简便方法计算(过程写出来):7/9+(2/3-4/9)= 12/5-(5/6+2/5)= 13/15-5/12-1/12+2/15=

问题描述:

简便方法计算(过程写出来):7/9+(2/3-4/9)= 12/5-(5/6+2/5)= 13/15-5/12-1/12+2/15=

7/9-4/9+2/3=1/3+2/3=1
12/5-2/5-5/6=2-5/6=7/6
13/15+2/15-(5/12+1/12)=1-1/2=1/2