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3*x1 + 4*x2 = 7 3*x3 + x1 + 2*x2 = 6 x3 + x1 - x2 = 1
3*x1 + 4*x2 = 7 x1 + 2*x2 + 3*x3 = 6 x1 - x2 + x3 = 1
$$3 x_{1} + 4 x_{2} = 7$$<br><br>$$3 x_{3} + x_{1} + 2 x_{2} = 6$$<br><br>$$x_{3} + x_{1} - x_{2} = 1$$