Find the missing rule in the pattern: Input -> Intermediate Value -> Output. The second step is adding 5. Examples: 2->11, 4->17, 6->23. Options: A) +4, B) +8, C) x2, D) x3

The pattern is: Input $\xrightarrow{\text{Missing Rule}} \text{Intermediate Value} \xrightarrow{+5} \text{Output}$.
We can find the intermediate value by reversing the "+5" operation, which means subtracting 5 from the output.

• For input 2, the output is 11. Intermediate Value for 2: $11 - 5 = 6$. So, $2 \xrightarrow{\text{Missing Rule}} 6$.

• For input 4, the output is 17. Intermediate Value for 4: $17 - 5 = 12$. So, $4 \xrightarrow{\text{Missing Rule}} 12$.

• For input 6, the output is 23. Intermediate Value for 6: $23 - 5 = 18$. So, $6 \xrightarrow{\text{Missing Rule}} 18$.

We observe the following transformations:

$$2 \to 6$$ $$4 \to 12$$ $$6 \to 18$$

In each case, the intermediate value is obtained by multiplying the input value by 3.

$$2 \times 3 = 6$$ $$4 \times 3 = 12$$ $$6 \times 3 = 18$$

Therefore, the missing rule is $\times 3$.

Comparing our finding with the given options:
A) +4
B) +8
C) $\times 2$
D) $\times 3$
The correct option is D.

The final answer is $\boxed{\text{D) } \times 3}$.