帮算到解方程组的数学题！

7X-3Y=-1 (1)
4X-5Y=-17 (2)
(1)*5
35x-15y=-5 (3)
(2)*3
12x-15y=-51 (4)
(3)-(4)
23x=46
x=2

把x=2代入(1)
14-3Y=-1
Y=5

X=2
Y=5

2.
10X+3Y+1=0 (1)
4X+5Y+8=0 (2)
(1)*5
50X+15Y+5=0 (3)
(2)*3
12X+15Y+24=0 (4)
(3)-(4)
38X-19=0
X=1/2
把X=1/2代入(1)
5+3Y+1=0
Y=-2

X=1/2
Y=-2

3.
3A=5B (1)
2A-3B=1 (2)
(1)*2
6A-10B=0 (3)
(2)*3
6A-9B=3 (4)
(4)-(3)
B=3
把B=3代入(1)
3A=15
A=5

A=5
B=3

28x-12y=-4
28x-35y=-119
y=5 x=2

50x+15y=-5
12x+15y=-24
x=1/2 y=-2

B=3 A=5

1.X=2 Y=5
2.X=0.5 Y=-2
3.A=5 B=3