The expression $3(x + y)$ can be simplified by distributing the 3 to both $x$ and $y$:

$3(x + y) = 3x + 3y$

Let me know if you'd like more details or have any questions!

Here are 5 related questions to explore:

1. How would you simplify $5(x + 2y)$?
2. What happens when you distribute $-4(x + 3)$?
3. Can you factor the expression $6x + 6y$ back into a form similar to $3(x + y)$?
4. What if $x = 2$ and $y = 5$, how would you evaluate $3(x + y)$?
5. How do you distribute constants in expressions with more than two terms, like $2(x + y + z)$?

Tip: Always remember to apply the distributive property correctly by multiplying the outer term with each term inside the parentheses.