If $x+1=y-8$ and $x=2 y$, then the value of $x+y$ is
(A) -18
(B) 0
(C) -9
(D) -27
(E) -36
Since $x+1=y-8$ and $x=2 y$, then $2 y+1=y-8$ or $y=-9$.

Thus, $x=2(-9)=-18$, and so $x+y=(-9)+(-18)=-27$.

ANSWER: (D)