1又1/4+(-6.5)+3又3/8+(-1.25)+5/28=1.25-6-1/2 +3+3/8-1.25+5/28 (消去1.25与-1.25,合并-1/2和3/8,-6和3)=-3+1/4+5/28 (通分)=-3+(7+5)/28=-3+12/28=-3+3/7=-2又4/7