13分之7乘负9加13分之7乘负18加13分之7=7/13×(-9)+7/13×(-18)+7/13=7/13×(-9-18+1)=7/13×(-26)=-14负19乘0.25加4分之1乘负7加负4分之1乘负2=-19×0.25+1/4×(-7)+(-1/4)×(-2)=(-19)×1/4+1/4×(-7)+1/4×2=1/4...