#### Answer

$\color{blue}{(-\infty, -6)}$

#### Work Step by Step

The given inequality is "$x$ is less than $-6$."
The numbers included in this set are the numbers that are less than $-6$, which are to the left of $-6$ on the number line.
The equivalent interval notation of the given inequality will have:
$\bf\text{lower limit:}$
none, so negative infinity will be used.
$\bf\text{upper limit:}$
$-6$, but a parenthesis will be used since $-6$ is not included
Therefore, the interval is: $\color{blue}{(-\infty, -6)}$