简便方法计算 3/10-(3/4-7/10)= 5/9+(4/5+4/9)=

问题描述:

简便方法计算 3/10-(3/4-7/10)= 5/9+(4/5+4/9)=

3/10-(3/4-7/10)= 3/10-3/4+7/10=1-3/4=1/4
5/9+(4/5+4/9=5/9+4/9+4/5=1+4/5=1.8
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