What is the perimeter of a rectangle formed by combining two squares with a perimeter of 12 decimeters?
用两个周长12分米的正方形，拼成的长方形的周长是多少分米．
<gadget id="calculator">12 / 4</gadget>
<output>3</output>

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

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

<result>18</result>