In the image, the expression shown is $2x + x + 6$. To simplify this expression, we combine like terms:

1. Combine the $x$-terms: $2x + x = 3x$

2. The constant term $+6$ remains as it is.

So, the simplified expression is: $3x + 6$

The correct answer to select is therefore: 3x + 6

Would you like more details on how to simplify algebraic expressions?

Here are five related questions for further exploration:

1. How do you simplify expressions with more complex terms, like $4x + 3x + 5 + 2$?
2. What are like terms, and why is it important to combine them?
3. How do we handle expressions with both positive and negative coefficients?
4. What are algebra tiles, and how can they visually represent equations?
5. How would this approach change with an equation instead of an expression?

Tip: When simplifying expressions, always look for like terms (terms with the same variable and exponent) to combine for a cleaner, simpler expression.