跪求30道数学题目！！！

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一.解方程
1.2x+9y=81
3x+y=34

2.9x+4y=35
8x+3y=30

3.7x+2y=52
7x+4y=62

4.4x+6y=54
9x+2y=87

5.2x+y=7
2x+5y=19

6.x+2y=21
3x+5y=56

7.5x+7y=52
5x+2y=22

8.5x+5y=65
7x+7y=203

9.8x+4y=56
x+4y=21

10.5x+7y=41
5x+8y=44

二.化简
1．3ab-4ab+8ab-7ab+ab=______．

2．7x-(5x-5y)-y=______．

3．23a3bc2-15ab2c+8abc-24a3bc2-8abc=______．

4．-7x2+6x+13x2-4x-5x2=______．

5．2y+(-2y+5)-(3y+2)＝______．

6．(2x2-3xy+4y2)+(x2+2xy-3y2)=______．

7．2a-(3a-2b+2)+(3a-4b-1)=______．

8．-6x2-7x2+15x2-2x2＝______．

9．2x-(x+3y)-(-x-y)-(x-y)＝______．

10．2x+2y-[3x-2(x-y)]=______．

11．5-(1-x)-1-(x-1)=______．

12．( )+(4xy+7x2-y2)=10x2-xy．
三.计算
1. 3/7 × 49/9 - 4/3
2. 8/9 × 15/36 + 1/27
3. 12×