The big clock on the square strikes 5 times at 5 o'clock, it takes 8 seconds to finish the knocking, and 12 times at 12 o'clock, how many seconds does it take to finish the knocking.
广场上的大钟5时敲5下，8秒敲完，12时敲12下，需多少秒敲完．
<gadget id="calculator">12 - 1</gadget>
<output>11</output>

<gadget id="calculator">5 - 1</gadget>
<output>4</output>

<gadget id="calculator">8 / 4</gadget>
<output>2</output>

<gadget id="calculator">11 * 2</gadget>
<output>22</output>

<result>22</result>