To use the associative property to group like terms together in the expression \( 9x + (2x + 3) \), we can rearrange the terms without changing the sum.
The expression can be rewritten as:
\[ (9x + 2x) + 3 \]
Here, we have grouped the like terms \( 9x \) and \( 2x \) together.
So the expression, with like terms grouped, is:
\[ (9x + 2x) + 3 \]