x - y = - 11   .............( 1 ) 
y + 7 = - 2x ...............( 2 )
from equation ( 1 ) 
x - y = - 11
x   = -11 + y  ...........( 3)      
putting x in equation  ( 2 ) 
y + 7 = - 2 x  
y  + 7 = -2 ( -11 + y )             y + 7 = 22 - 2 y                       y + 2 y =22 - 7            
3 y = 15                  y = 15 / 3 
putting value of y in equation 3 
x   = -11+ ( 13 /5 )                       x = -33 /3 + 15 / 3         ( l.c.m)
x  = -17 / 5                       
check       
 x = -11 + y 
- 17 / 5 = -11 + 13 / 5 
-17 /5   = -17 / 5