Question 271088
9x-3z=20
3x+6z=2

A.Choose a variable to eliminate first. In this example, y will be eliminated.

B. Multiply the equations so that there is the same number of that variable in both equations. Find the least common multiple (LCM) of the coefficients of the variable you chose to eliminate. Multiply the equations accordingly so that both of the coefficients are of the same value, except one is negative.
The LCM would be six seen as 3x+6z=2 and six is the LCM
Multiply first equation by two.
2(9x-3z=20)
18x-6z=40

C. Now add the equations leaving out the variable with z in it.

 18x-6z=40
+3x+6z=2
___________
21x=42
x=2

D.  Solve for the remaining variable. This can be done using any methods to solve for a one-variable equation.
 
9(2)-3z=20
18-3z=20
-3z=2
z=-2/3

I believe you said you had the same answer so I don't know why you say it's wrong.