Question 785867
x + 2y - z = 5
2x - y + z = 2
        y + z = 2
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x + 2y - z = 5
2x - y + z = 2
---------------- Add
3x + y = 7  Eqn A
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x + 2y - z = 5
     y + z = 2
------------------ Add
x + 3y = 7 Eqn B
9x + 3y = 21  Eqn A times 3
------------------------------ Subtract
-8x = -14
x = 7/4
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x + 3y = 7 Eqn B
3y = 21/4
y = 7/4
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y + z = 2
z = 1/4