\[\boxed{\text{646\ (645).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[\left\{ \begin{matrix} x^{2} - y^{2} = 30 \\ x + y = 5\ \ \ \ \ \\ \end{matrix} \right.\ \Longrightarrow \left\{ \begin{matrix} (x + y)(x - y) = 30 \\ x + y = 5\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \\ \end{matrix} \right.\ \Longrightarrow\]
\[\Longrightarrow \left\{ \begin{matrix} x - y = 6 \\ x + y = 5 \\ \end{matrix} \right.\ \Longrightarrow \left\{ \begin{matrix} 2x = 11\ \ \\ y = 5 - x \\ \end{matrix} \right.\ \Longrightarrow \left\{ \begin{matrix} x = 5,5\ \ \ \\ y = - 0,5. \\ \end{matrix} \right.\ \]
\[Ответ:\ \ (5,5;\ - 0,5).\]