The clock strikes 4 times at 4 o'clock, and it takes 6 seconds to finish knocking, then 10 times at 10 o'clock, how many seconds to finish knocking.
时钟4点钟敲4下，6秒钟敲完，那么10点钟敲10下，多少秒钟敲完．
<gadget id="calculator">4 - 1</gadget>
<output>3</output>

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

<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<gadget id="calculator">2 * 9</gadget>
<output>18</output>

<result>18</result>