It took 3 seconds for Xiaojun’s wall clock to strike 2 times at 2 o’clock, and 7 times at 7 o’clock, how many seconds did it take?
小军家的挂钟2点时敲2下，用了3秒钟，7点时敲7下，要用多少秒钟？
<gadget id="calculator">2 - 1</gadget>
<output>1</output>

<gadget id="calculator">3 / 1</gadget>
<output>3</output>

<gadget id="calculator">7 - 1</gadget>
<output>6</output>

<gadget id="calculator">3 * 6</gadget>
<output>18</output>

<result>18</result>