Real numbers \((x,y)\) satisfy the following equations:
\[
(x + 3)(y + 1) + y^2 = 3y
\]
\[
-x + x(y + x) = - 2x - 3.
\]
Find the sum of all possible values of \(x\).

Let's think step by step and output the final answer within \boxed{}.
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