At 3 o'clock on a large clock, it took 6 seconds from the first sound to the last sound, how many seconds will the clock sound at 8 o'clock.
一大钟3点时，从响第一声到最后一声用了6秒，8点时钟会响多少秒．
<gadget id="calculator">3 - 1</gadget>
<output>2</output>

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

<gadget id="calculator">8 - 1</gadget>
<output>7</output>

<gadget id="calculator">3 * 7</gadget>
<output>21</output>

<result>21</result>