[tex]\bf \begin{cases}
-x^2-x+19=\boxed{y}\\
x=\boxed{y}+80\\
----------\\
x=\boxed{-x^2-x+19}+80
\end{cases}
\\\\\\
x+x+x^2-19-80=0\implies
\begin{array}{lcclll}
x^2&+2x&-99&=0\\
&\uparrow &\uparrow \\
&11-9&11\cdot -9
\end{array}
\\\\\\
(x+11)(x-9)=0\implies
\begin{cases}
x+11=0\implies &x=-11\\
x-9=0\implies &x=9
\end{cases}[/tex]
