It takes 8 minutes to fry one cake in a pan (4 minutes for the front and 4 minutes for the reverse side), and you can fry 3 cakes each time. How many minutes does it take to cook 7 cakes?
用一口平底锅煎饼，煎一张饼需要8分钟(正、反面各4分钟)，每次可以煎3张，煎7张饼需要多少分钟．
<gadget id="calculator">4 * 3</gadget>
<output>12</output>

<gadget id="calculator">8 + 12</gadget>
<output>20</output>

<result>20</result>