The expression given is:

$2c - 12 + 6d$

Since no specific instructions are given (like solving for a variable or simplifying further), this expression is already in its simplest form. The terms cannot be combined because they contain different variables or are constants.

Final simplified expression:

$2c - 12 + 6d$

If you'd like to perform additional steps, like solving for $c$ or $d$ given some values, let me know.

Would you like more details or have any further questions?

Here are 5 related questions for further exploration:

1. What happens when you assign specific values to $c$ and $d$?
2. How do you solve for $c$ or $d$ when the expression is set equal to a number?
3. Can you factor the expression, if possible?
4. What is the significance of the coefficients in each term?
5. How would you represent this expression graphically?

Tip: Always look for like terms (terms with the same variable or constants) to simplify expressions further!