Question 250243
3x+3y+6z=9 --> x+y+2z=3
2x+y+3z=7
x+2y-z=-10 
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For this problem, use eqn 1 to eliminate x from the other 2:
x+y+2z=3 Eqn 1
x+2y-z=-10 Eqn 3
---------- Subtract
-y + 3z = 13  Eqn A
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2x+y+3z=7 Eqn 2
2x+2y+4z=6 Eqn 1 times 2
----------- Subtract
-y -z = 1 Eqn B
-y+3z = 13 Eqn A
--------------- Subtract
-4z = -12
z = 3
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Sub for z, find y
Sub for y and z, find x