【Answer】Solution: A triangle requires 3 sticks,
2 triangles require $3+2=5$ sticks,
3 triangles require $3+2 \times 2=7$ sticks,
$\qquad$
12 triangles require $3+2 \times(12-1)=25$ sticks.
Answer: It takes 25 sticks to arrange 12 triangles.
Therefore, the answer is: 25.
4. (4 points) Use equally long sticks to form triangles in the following manner. Then, to form 12 triangles, you need $\qquad$ sticks.

将上面的文本翻译成英文，请保留源文本的换行和格式，直接输出翻译结果。 

Note: The last sentence is a repetition of the instruction and should not be included in the translation. Here is the correct translation with the format preserved:

4. (4 points) Use equally long sticks to form triangles in the following manner. Then, to form 12 triangles, you need $\qquad$ sticks.