A wall clock takes 6 seconds to strike 3 times, how many seconds does it take to strike 9 times?
一只挂钟，敲3下要6秒，敲9下要多少秒．
<gadget id="calculator">3 - 1</gadget>
<output>2</output>

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

<gadget id="calculator">9 - 1</gadget>
<output>8</output>

<gadget id="calculator">3 * 8</gadget>
<output>24</output>

<result>24</result>