(someone )

solve the system by substitution. ( explain how you did it ill give brainliest)

-x-y-z=-8
-4x+4y+5z=7
2x+2z=4

{x,y,z} = {0,13,20}

Step-by-step explanation:

 x + y - z = -7

  [2]    2x - y + z = 7

  [3]    x - 4y + 3z = 8

Solve by Substitution :

// Solve equation [3] for the variable  x  

 [3]    x = 4y - 3z + 8

// Plug this in for variable  x  in equation [1]

  [1]    (4y-3z+8) + y - z = -7

  [1]    5y - 4z = -15

// Plug this in for variable  x  in equation [2]

  [2]    2•(4y-3z+8) - y + z = 7

  [2]    7y - 5z = -9

// Solve equation [2] for the variable  y  

 [2]    7y = 5z - 9

 [2]    y = 5z/7 - 9/7

// Plug this in for variable  y  in equation [1]

  [1]    5•(5z/7-9/7) - 4z = -15

  [1]     - 3z/7 = -60/7

  [1]     - 3z = -60

// Solve equation [1] for the variable  z  

  [1]    3z = 60  

  [1]    z = 20  

// By now we know this much :

   x = 4y-3z+8

   y = 5z/7-9/7

   z = 20

// Use the  z  value to solve for  y  

   y = (5/7)(20)-9/7 = 13  

// Use the  y  and  z  values to solve for  x  

 x = 4(13)-3(20)+8 = 0  

Solution :

{x,y,z} = {0,13,20}  

Solve for x in 2x + 2x = 4

x = 2 - z

Substitute x = 2 - z into -x - y - z = -8

-2 - y = -8

Substitute x = 2 - z into -4x + 4y + 5z = 7

-8 + 9z + 4y = 7

Solve for y in -2 - y = -8

y = 6

Substitute y = 6 into -8 + 9z + 4y = 7

9z + 16 = 7

Substitute y = 6 into x = 2 - z

x = 2 - z

Solve for z in 9z + 16 = 7

z = -1

Substitute z = - 1 into x = 2 - z

x = 3

Therefore,

x = 3

y = 6

z = -1

check above link.

graphically?   well, you graph them both, the solutions is where they both intersect each other, since there are two solutions, meaning they will meet twice, or namely the linear will run into the quadratic curve twice, and where they meet, those x,y coordinates are the solutions to the system.