A piece of wood, Master Wang needs to saw it into 8 sections, each section takes 3 minutes, how many minutes will it take to saw all of them.
一根木料，王师傅要把它锯成8段，每锯开一段需要3分钟，全部锯完需要多少分钟．
<gadget id="calculator">8 - 1</gadget>
<output>7</output>

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

<result>21</result>