简便运算:21/【(2/3+2/5)*30/(3又5/42-2又5/14)】 详细过程

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简便运算:21/【(2/3+2/5)*30/(3又5/42-2又5/14)】详细过程简便运算:21/【(2/3+2/5)*30/(3又5/42-2又5/14)】详细过程简便运算:21/【(2/3+2/

简便运算:21/【(2/3+2/5)*30/(3又5/42-2又5/14)】 详细过程
简便运算:21/【(2/3+2/5)*30/(3又5/42-2又5/14)】 详细过程

简便运算:21/【(2/3+2/5)*30/(3又5/42-2又5/14)】 详细过程
21/{(2/3+2/5)*30/[(3+5/42)-(2+5/14)]}
=21/{(30*2/3+30*2/5)/[(3-2)+(5/42-5/14)]}
=21/[(20+12)/(1-5/21)]
=21/[32/(16/21)]
=(21*16/21)/32
=16/32
=1/2