To simplify the expression:

$6a - 4 + 6a^2 + 6 - 2a$

Let's follow these steps:

1. Combine the like terms involving $a$: $6a - 2a = 4a$

2. The constant terms: $-4 + 6 = 2$

So the expression simplifies to:

$6a^2 + 4a + 2$

Would you like more details on this process or have any other questions? Here are some related problems you might find useful:

1. Simplify $8x - 3 + 7x^2 + 5 - 4x$.
2. Factor $6a^2 + 4a + 2$.
3. Expand $(3a + 2)(2a - 1)$.
4. Simplify $10b + 3 - 5b + 2b^2 + 1$.
5. Combine like terms in $9y^2 - 4y + 2y + 5 - 3$.
6. Solve $6a^2 + 4a + 2 = 0$ using the quadratic formula.
7. Find the derivative of $6a^2 + 4a + 2$ with respect to $a$.
8. Evaluate the expression $6a^2 + 4a + 2$ when $a = -1$.

Tip: When simplifying, always start by combining like terms, which helps to reduce the expression to its simplest form.