Answer
$a\lt -6 $ or $ a \geq -3$
The graph is shown below.
Work Step by Step
$a$ is fewer than $-6$.
$\Rightarrow a\lt -6$
or
$a$ is no less than $-3$.
$\Rightarrow a\geq -3$
The compound inequality is
$a\lt -6 $ or $ a \geq -3$
Graph the union of the graphs of $a\lt -6$ and $a\geq -3$.