7.2几百几十加减几百几十笔算笔算下列各题：320+210=560+110=250+220=370+120=840+160=770+240=480+230=330+390=450+470=390+250=550+390=190+250=360+250=440+180=780250=360120=440130=660250=360270=710230=420130=370280=250160=520140=960580=630250=760290=550290=310120=440-250=答案：320+210=530560+110=670250+220=470370+120=490840+160=1000770+240=1100480+230=710330+390=720450+470=920390+250=640550+390=940190+250=440360+250=610440+180=620780250=530360120=240440130=310660250=410360270=90710230=480420130=290370280=90250160=90520140=380960580=360630250=380760290=470550290=260310120=190440-250=190