To use the associative property to group like terms in the expression \(9x + (2x + 3)\), we can rearrange the terms without changing their order. The associative property states that the way we group numbers in an addition or multiplication operation does not change their sum or product.
We can group the like terms (the terms involving \(x\)) together:
\[ (9x + 2x) + 3 \]
So, the expression \(9x + (2x + 3)\) can be grouped as \((9x + 2x) + 3\).