It takes 12 minutes to saw a section of steel into 3 sections. According to this calculation, how many minutes will it take to saw it into 4 sections?
一段钢材，锯成3段需12分钟，照这样计算，锯成4段需多少分钟．
<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<gadget id="calculator">4 - 1</gadget>
<output>3</output>

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

<result>18</result>