3.75－｛负二分之一＋四又三分之二－负二分之一＋六分之一｝=3.75-{-1/2+4+2/3-(-1/2)+1/6}=3.75-{4+5/6}=3.75-4-5/6=-0.25-5/6=-1/4-5/6=-(3+10)/12=-13/12