Ok so I don't know I can do them but sometimes I get one variable wrong but the other two are correct, maybe I'm mixing up the equations or numbers?


7x+5y+z=0
-x+3y=2z=-16
x-6y-z=-18



3x-5y+z=9
x-3y-2z=-8
5x-6y+3z=15


4x-3y+2z=12
x+y-z=3
-2-2y+2z=5

-x-3y+z=54
4x+2y-3z=-32
2y+8z=78

You have to solve for a variable first. Tip: Solve for the easiest one. For example in your first one, I'd sovle for z and use this equation.

7x+5y+z=0
-7x -7x
--------------------
5y+z=-7x
-5y -5y
----------------------
z=-7x-5y

Now plug that into the other equations:

-x+3y=2z=-16
x-6y-z=-18

The way to know if your answers are correct are try plugging them in once you have found all the variables.

Edit: I noticed in your first problem that theirs 2 equation signs in "-x+3y=2z=-16." Assuming it is not a typo, you could just do the following to find z.

2z=-16
z=-8

Can you show us the work you've done? It would help to straighten out the issue you're having.

Quote:

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I don't know I can do them but sometimes I get one variable wrong but the other two are correct, maybe I'm mixing up the equations or numbers?

7x+5y+z=0
-x+3y=2z=-16
x-6y-z=-18

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It sounds like you do know how to do them, but you make mistakes. Nearly everyone does that. That's why you substitute back into all of the equations once you find a solution.

Have you learned Cramer's Rule yet? For me, that simplifies the type of equation you've got -- but you can even make mistakes with that.