HELP! how to solve system of equations

Question

x-2y+z=-1

y+2z=-4

x+y+3z=-5

Answer 1

Given system of equations are x - 2y + z = -1 ==>1

                                                 y + 2z = -4 ==>2

                                                 x + y + 3z = -5 ==>3

Substract equation 1 from 3

x - 2y + z = -1

x + y + 3z = -5

(-) (-)  (-)     (+)

    -3y - 2z = 4 ==>4

Add equation 2 and 4

y + 2z = -4 ==>2

-3y - 2z = 4 ==>4

-2y         = 0

-2y = 0

-y = 0

y = 0

Substitute y value in equation 2

y + 2z = -4 ==>2

0+ 2z = -4

2z = -4

z = -2

Substitute y and z value in equation 1

x - 2y + z = -1 ==>1

x - 2(0) + (-2)= -1

x - 0 - 2 = -1

x - 2 = -1

x = 2 - 1

x = 1

Therefore the solution of the given system of equations is x = 1 , y = 0 , z = -2