\[\left\{ \begin{matrix} 3k + b = 8\ \ \ \\ - 4k + b = 1 \\ \end{matrix} \right.\ ( - )\]
\[7k = 7\]
\[k = 1.\]
\[b = 8 - 3k = 8 - 3 = 5.\]
\[Уравнение\ прямой:\]
\[y = x + 5.\]
\[Ответ:y = x + 5.\]