\[\frac{11 - x}{8} - \frac{12 - x}{4} < 0\ \ \ | \cdot 8\]
\[11 - x - 2 \cdot (12 - x) < 0\]
\[11 - x - 24 + 2x < 0\]
\[x < 13\]
\[Ответ:\ \ 12.\]