[x-2y=5,50x-30y=5]
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[x-2y=5,50x-30y=5][x-2y=5,50x-30y=5][x-2y=5,50x-30y=5]x-2y=5(1)50x-30y=5(2)由（1）得：x=5+2y（3）把（3）带入（2）得
[x-2y=5,50x-30y=5]
[x-2y=5,50x-30y=5]
[x-2y=5,50x-30y=5]
x-2y=5 (1)
50x-30y=5 (2)
由（1）得：x=5+2y （3）
把（3）带入（2）得：
50×（5+2y）-30y=5
化简: 250+100y-30y=5
移项并合并同类项:70y=-245
化系数为一:y=-3.5
把y=-3.5带入（1）得：x=-2
所以这个方程组的解是 x=-2, y=-3.5
x-2y=5
50x-30y=5
所以x=-2 y=-7/2
所以解集是{(-2,-7/2)}
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