｛5/2-（3/8+1/6-3/4）×24｝/5×(-1) =[5/2-(3/8)*24+(1/6)*24-(3/4)*24]/5*(-1)=(5/2-9+4-18)/5*(-1)=(5/2-23)/5*(-1)=(1/2-23/5)*(-1)=(0.5-4.6)*(-1)=4.1
-1.5
