题干
口算
50+80=____ 30+90=____ 50+50=____ 40+70=____
90+80=____ 80-70=____ 100+300=____ 800-400=____
900-100=____ 70+50=____ 70-30=____ 100-10=____
答案(点此获取答案解析）
130,120,100,110,170,10,400,400,800,120,40,90
