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原式=(-2/3)+(1/4)-(1/6)-(1/2) =(-8/12)+(3/12)-(2/12)-(6/12) =(-8+3-2-6)/12 =-13/12原式=-8-(7/2)+2-(1/2)+12 =6-4 =2原式=-3.75+2.75 =-1原式=(-2/3)+1.75-(1/3)-1.75 =-1原式=(-3又2/3)+2.75+(1又2/3)+1.75 =-2+4.5 =2.5 8.原式=【31/2-(5/4÷7/5+7/2)】÷(-9/8) =【31/2-(5/4×5/7+7/2)】×(-8/9) =【31/2-(25/28+7/2)】×(-8/9) =(31/2-25/28-7/2)×(-8/9) =(24/2-25/28)×(-8/9) =(336/28-25/28)×(-8/9) =311/28×(-8/9) =-622/63
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