You can only bake 2 cakes in a pan each time, and both sides must be baked. It takes 2 minutes to bake each side, and how many minutes is the minimum time to bake 9 cakes.
用平底锅烙饼，每次只能烙2张，两面都要烙，烙好每面需要2分钟，烙好9张最少需要多少分钟．
<gadget id="calculator">6 / 2</gadget>
<output>3</output>

<gadget id="calculator">2 * 2 * 3</gadget>
<output>12</output>

<gadget id="calculator">2 * 3</gadget>
<output>6</output>

<gadget id="calculator">12 + 6</gadget>
<output>18</output>

<result>18</result>