help please

Question

use either substitution or addition to solve this system of linear equations:

2x-y+4z=7

x+2y+6z=3

-3x-3y+2z=-8

Answer 1

First label your equations, 1, 2, 3. Then chose one of the u=variables that you would like to get rid off for the time being. For example get rid of 'y' by adding equations 1 and 2. To do so multiply equation 1 by 2, you should get 

6x + 14z = 17....label this 4

 

Then add equations 1 and 3. Get rid of the variable 'y' by multiplying equation 2 by -3. You should get the answer

-9x - 10z = -29....label this 5

 

Then add your new equations 4 and 5. I chose to get rid of 'x' first. So multiply equation 4 by 6 and equation 5 by 4. You should get z= -7/22.

 

Substitute the value of z in either equation 4 or 5. Then you'll get the answer for 'x'. Finally substitute the value you got for z and x to find y in either equation 1, 2 or 3.