\[\boxed{\text{890\ (890).\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[y = 1,5x - 3;\ \ \ \ y = 2,5x + 1\]
\[1,5x - 3 = 2,5x + 1\]
\[- x = 4\]
\[x = - 4\]
\[y( - 4) = - 6 - 3 = - 9.\]
\[y = 5x + b\]
\[5 \cdot ( - 4) + b = - 9\]
\[- 20 + b = - 9\]
\[b = 11\]
\[Ответ:b = 11.\]