\( 5(x+9) \) when \( x=3 \)

To solve \( 5(x+9) \) when \( x=3 \), simply substitute 3 for \( x \) in the equation. So, it becomes \( 5(3+9) \), which simplifies to \( 5(12) \). Finally, multiply it out to get \( 60 \). If you’re ever stuck on a similar problem, just remember to break it down step by step! Always substitute first, perform the operations in parentheses, and then multiply or divide as needed. Common mistakes often occur if one forgets to properly follow the order of operations.