It takes 3 minutes to saw a piece of wood into 8 sections, how many minutes will it take to complete the sawing?
把一根木头锯成8段，每锯下一段需要3分钟，锯完一共需要多少分钟．
<gadget id="calculator">8 - 1</gadget>
<output>7</output>

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

<result>21</result>