①+= ③ -=
②+= ④ -=
亮亮折纸飞机,已经折了20架,( ),亮亮一共要折多少架飞机?
①给明明9架( )
②还要折8架( )
12-4= 7+8= 17-8= 16-8= 13-9=
16-7= 12-3= 10+9= 17-6= 7+9=
48-40= 30+5= 62-60= 50+3= 54-50=
24-4= 46-6= 4+40= 70+6= 70+5=