简便计算:7.5*[63.9/(7-2.5)]

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简便计算:7.5*[63.9/(7-2.5)]

简便计算:7.5*[63.9/(7-2.5)]
简便计算:7.5*[63.9/(7-2.5)]

简便计算:7.5*[63.9/(7-2.5)]
7.5*[63.9/(7-2.5)]
=7.5/7.5*{[63.9/(7-2.5)]/7.5}
=(63.9/4.5)/7.5
=(639/45)*4/(7.5*4)
=639/45*4/30
=639*4/(45*30)
=213*4/(45*10)
=213/45*2.5
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