尽量省略括号和加号!计算四道题,

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1、=27-18-7-32=(27-7)-(18+32)=20-50=-302、=1/3-1/5-1+2/3=(1/3+2/3-1)-1/5=0-1/5=-1/53、=0.5-1/4+2.75+1/2=(0.5+1/2)+(2.75-1/4)=1+2.5=3.54、=-2/3-1/6+1/4-1/2=1/4-(2/3+1/6+1/2)=1/4-4/3=-13/12