If only 2 cakes can be placed in one pan, each cake needs to be baked on both sides, each side is baked for 3 minutes, and 9 cakes are to be baked, how many minutes will it take at least.
如果一口锅只能放2张饼，每张饼都要烙两面，每面烙3分钟，要烙9张饼，至少需要多少分钟．
<gadget id="calculator">3 * 2 * 3</gadget>
<output>18</output>

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

<gadget id="calculator">18 + 9</gadget>
<output>27</output>

<result>27</result>