If it takes 9 minutes to saw a piece of wood into 4 sections, how many minutes will it take to saw 8 sections?
把一根木材锯成4段需9分钟，锯8段用多少分钟．
<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">9 / 3</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>