[tex]\begin{array}{lrlll}
x+y=-4&\times -1\implies &-x-y=4\\
x+2y=13&\implies &\ x+2y=13\\
&&\textendash\textendash\textendash\textendash\textendash\textendash\textendash\textendash\textendash\textendash\textendash\\
&&\boxed{?}+\boxed{?}=\boxed{?}
\end{array}[/tex]
