How do i solve this three variable equation

2x - 6y + z = 30      (1st)
-x + 3y + 2z = -20 (2nd)
-6x - 5y + 6z = 7   (3rd)

from (2nd)  you have:
-x + 3y + 2z = -20 
 x = 3y + 2z + 20

substitute x = 3y + 2z + 20 into  (1st) 2x - 6y +z = 30

2x - 6y + z = 30
2(3y + 2z + 20) - 6y +z = 30
6y + 4z + 40 - 6y + z = 30
5z + 40 = 30
5z = -10
  z = -2

plug in z = - 2 into (2nd) and  (3rd)

-x + 3y + 2(-2) = -20 (2nd)
-x + 3y = -16 so x = 3y + 16

-6x - 5y + 6z = 7   (3rd)
-6x -5y +6(-2) = 7
-6x - 5y = 19

substitute x = 3y + 16 into -6x - 5y = 19

-6x - 5y = 19
-6(3y + 16) - 5y = 19
-18y - 96 - 5y = 19
-23y = 115
     y = -5

x = 3y + 16
x = 3(-5) + 16
x = -15 + 16
x = 1

answer
x = 1, y = -5 and z = -2

Here, feel free to ask if there are any questions