商店有50辆小汽车,卖出20辆,_______?
小明拿50元买一个 ,需要找回10元( )
50-30=
100-60=
60-40=
100-70=
70-50=
100-80=
80-60=
100-90=
90-70=
50–30= 60–40= 40–40= 10+20=
50+50= 60–30= 40+50= 80–30=
100–20= 60+20= 40+30= 40–10=
50+10= 60–10= 40–20= 10+50=
50–50= 20+60= 70+20= 70–40=
30+20= 90–80= 20–20= 10+80=