2524 5565 10099 7887
4433 6886 60+629 2420+4
5650+4 86-807 55-550 4334
12+2= 12-2= 12×2=
12÷2= 30+5= 30-5=
50+3= 53-3= 7+40= 17-7=
8+10= 65-5= 3 +70= 39-9=
37-7= 68-8= 4+90= 30+8=
1+20= 90+7= 4+60= 99-9=
7+70= 66-6= 45-5= 20+9=
44-40= 76-6= 30+5= 50+7=
6+20= 93-90= 4+80= 83-3=
87-0= 96-6= 99-9= 80+9= 98-80= 22-2=
77-7= 74-70= 84-40= 55-5= 84-4= 98-8=
60+6= 4+60= 5+70= 48-8= 56-50= 78-50=
27-20= 30+2= 66-4= 8+50= 66-40= 40+5=
8+70= 87-7= 35-30= 66-6= 39-4= 6+20=
74-40= 1+60= 32+3= 86-80= 50+3= 40+2=
10+0= 5+7= 13﹣3= 11﹣10=
2+9= 8﹣4= 10+5= 3+7=
6+4= 9﹣9= 1+10= 10﹣4=
6+7﹣1= 8+2+2= 9﹣3﹣3=
10﹣6+5= 9+1﹣6= 18﹣3﹣5=

40+9= 6+70= 80+8=
9+40= 70+6= 8+80=
49-40= 76-6= 88-8=
49-9= 76-70= 88-80=
53=50+ 80=-4 69=+9
-7=30 53=50+ 70=-
>>>>
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口答:同学们一共要栽
棵树。