\(\begin{array}{l}
A = \left[ {a - 2;\,\,a} \right],\,\,\,B = \left[ { - 2;\,\,8} \right]\\
A\backslash B = \emptyset \Leftrightarrow \left[ \begin{array}{l}
a < - 2\\
a - 2 > 8
\end{array} \right. \Leftrightarrow \left[ \begin{array}{l}
a < - 2\\
a > 10
\end{array} \right..
\end{array}\)