The problem asks to find the expression that is equivalent to $3(9u)$.

1. Problem Description

The problem asks to find the expression that is equivalent to $3(9u)$.

2. Solution Steps

We can simplify the given expression using the associative property of multiplication.

$3(9u) = (3 \times 9)u = 27u$.

Let's examine the given options:

- $9u + 3$: This is not equivalent because it's an addition, not multiplication.

- $u + 12$: This is also not equivalent as it is an addition and not equal to $27u$.

- $(9 + u)3 = 3(9+u) = 27 + 3u$: This is not equivalent. It uses the distributive property correctly.

- $27u$: This is the same as our simplified expression.

3. Final Answer

$27u$