If three squares with side lengths of 3 cm are put together, what is the perimeter of the resulting rectangle?
把三个边长是3厘米的正方形拼在一起，组成的长方形的周长是多少厘米？
<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<gadget id="calculator">3 + 9</gadget>
<output>12</output>

<gadget id="calculator">12 * 2</gadget>
<output>24</output>

<result>24</result>