Question 120918
x-y=11
y=2x-8 now replace y with (2x-8) in the first equation & solve for  x.
x-(2x-8)=11
x-2x+8=11
-x=11-8
-x=3
x=-3 answer.
-3-y=11
-y=11+3
-y=14
y=-14 answer.
proof
-14=2*-3-8
-14=-6-8
-14=-14