Question 471513
3x + 7y = 19
    x+y=5
x=5-y
3(5-y)+7y=19
15-3y+7y=19
4y=4
y=1
x=4
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x+3y = 12
5x+y = 4 
x=12-3y
5(12-3y)+y=4
60-15y+y=4
14y=56
y=4
x=0..