To simplify the expression given in the image:

$-3x + 2x$

We combine like terms, which are both terms involving $x$.

$-3x + 2x = -x$

Thus, the simplified expression is:

$-x$

The correct answer is the option "-x".

Do you have any questions, or would you like more details on this?

Here are 5 related questions you might find interesting:

1. How do you simplify expressions with multiple variables?
2. What are like terms in algebra, and why are they important?
3. How would you simplify $4x - 3x + 7x$?
4. What is the distributive property in algebra?
5. How do you factor algebraic expressions?

Tip: When simplifying algebraic expressions, always combine like terms (terms that have the same variable and exponent).