Question 67796
X+Y=3
Y=-X+3
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X-Y=1
-Y=-X+1
Y=X-1 this is where you made your mistake. you neglected to change -y to +y by multiplying the equation by -1.
also you have a 6 instead of a y in your answer. 
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{{{graph( 300, 200, -6, 5, -5, 5, y = -x +3, y = x -1)}}} (graph 300x200 pixels, x from -6 to 5, y from -5 to 5, of TWO functions y = -x +3, y = x -1).