Mom bakes 5 cakes, only two cakes can be baked at a time, both sides need to be baked, each side takes 3 minutes, how many minutes can the cake be eaten at the fastest.
妈妈烙5张饼，每次只能烙两张，两面都要烙，每面3分钟，最快多少分钟可以吃到饼．
<gadget id="calculator">2 * 3</gadget>
<output>6</output>

<gadget id="calculator">6 + 3 + 3 + 3</gadget>
<output>15</output>

<result>15</result>