Do I use substitution to solve this equation?

Question

x=y-7

-y-2x=8

 

-y-2(y-7)=8

-y-2y-14=8

-3y-14=8

-3y-14+14=8+14

-3y=22

/-3=22/-3

y=7-1/3

 

this just doesn't work :(

Answer 1

 X = y -7 

- Y - 2X = 8

 

-x -7 - 2X = 8

 

-3x = 15

 

  X = -5 

  Y = -5 +7 = 2

 

 Test:

  -5 = -7 +2

 

-2 - 2( -5 ) = 8