The expression $(a + b)(x)$ represents the product of two terms: $(a + b)$ and $x$. To simplify this expression, you can distribute $x$ to both $a$ and $b$:

$(a + b)(x) = ax + bx$

So, the simplified expression is:

$ax + bx$

Would you like any further details or explanations?

Here are some related questions:

1. How would you factor a similar expression, $ax + bx$?
2. What is the result of $(a - b)(x)$?
3. How do you expand $(a + b)(x + y)$?
4. Can this distributive property be applied to more complex expressions?
5. What if $a$ and $b$ were specific numbers? How would the expression change?

Tip: The distributive property allows you to break down expressions into simpler parts, making it easier to solve or simplify equations.