The expression $4(x + 3)$ can be simplified by distributing the 4 across the terms inside the parentheses.

$4(x + 3) = 4 \cdot x + 4 \cdot 3 = 4x + 12$

So, the simplified form is $4x + 12$.

Would you like more details on distribution or have any further questions?

Here are 5 related questions to explore:

1. What happens if you distribute a negative number instead of 4?
2. How would you factor $4x + 12$ back into $4(x + 3)$?
3. What if you were asked to solve $4(x + 3) = 20$?
4. How do you apply the distributive property when there are two variables inside the parentheses?
5. Can you expand $4(x^2 + 3x + 2)$?

Tip: The distributive property is key for simplifying expressions and solving equations, especially when handling parentheses.