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I                x +  y +  z =  2
II              2x      - 3z =  0
III              x - 2y -  z = -1

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I + III = IV    2x -  y      =  1
3I + II = V     5x + 3y      =  6

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3IV + V        11x           =  9    | :11
                 x           = 9/11
in II            z           = 6/11
in I             y           = 7/11