简便运算(3-9/8+8/9)*21/13-169/56=?

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简便运算(3-9/8+8/9)*21/13-169/56=?简便运算(3-9/8+8/9)*21/13-169/56=?简便运算(3-9/8+8/9)*21/13-169/56=?=[3-(1+1/8

简便运算(3-9/8+8/9)*21/13-169/56=?
简便运算(3-9/8+8/9)*21/13-169/56=?

简便运算(3-9/8+8/9)*21/13-169/56=?
=[3-(1+1/8)+(1-1/9)]x21/13-(13/7-13/8)/13
=[(3-1/8-1/9)x21-13/7+13/8]/13
=(63-21/8-3/7-13/7+13/8)/13
=(63-1-16/7)/13
=(60-2/7)/13
=418/91