Разбираемся:
\[3x + 5 + (x + 5) = (1 - x) + 4\]
\[3x + 5 + x + 5 = 1 - x + 4\]
\[4x + 10 = 5 - x\]
\[4x + x = 5 - 10\]
\[5x = -5\]
\[x = -1\]
Ответ: -1