To find the common difference of an arithmetic sequence, subtract any term from the term that follows it.

In your sequence, the terms are:
$-11, -17, -23$.

Let's calculate the common difference:

$d = -17 - (-11) = -17 + 11 = -6$

Next, check the difference between the second and third terms:

$d = -23 - (-17) = -23 + 17 = -6$

Thus, the common difference $d$ is $-6$.

Would you like to explore more details or have any questions?

Here are 5 related questions to expand your understanding:

1. How do you find the $n$-th term of an arithmetic sequence?
2. What is the sum of the first $n$ terms of an arithmetic sequence?
3. How do you determine if a sequence is arithmetic?
4. How does changing the common difference affect the sequence?
5. How can you graph an arithmetic sequence?

Tip: The formula for the $n$-th term of an arithmetic sequence is $a_n = a_1 + (n-1) \cdot d$.