After cutting a rectangle in half, a square with a side length of 3 cm is left. What is the perimeter of the rectangle?
将一个长方形切下去一半后，剩下一个边长是3厘米的正方形，这个长方形的周长是多少？
<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<gadget id="calculator">6 + 3</gadget>
<output>9</output>

<gadget id="calculator">9 * 2</gadget>
<output>18</output>

<result>18</result>