I have these equations, I need to figure out how to show how I got the answer that a could be 2 if x=2, y=0 and b=b ( I ran it in a computer program) I know I have to use Gauss elinimination but how??? :

{x-y+a*z=1, 2*x-y+z=-1, a*x+y-z=1};

{x-y+a*z=1, 2*x-y+z=-1, a*x+y-z=1};

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