连加连减:5+7+3=???????????????12+3+4=???????????14-2-5=??????????17+1-3=2+12+3=??????????????18-3+3=????????????12+6+3=?????????14+2+1=????15-4+3=???????????????19-6-4=????????????16+3-2=??????????11+2-5=??20-7-3=????????????????17-2+6=???????????14-3+8=??????????14-2-1=16+2+4=???????????????11-3+5