Workers install a batch of electric poles, 12 poles per day, and it can be completed in 30 days. If 6 more poles are installed every day, how many days can it be completed?
工人装一批电杆，每天装12根，30天可以完成，如果每天多装6根，多少天能够完成？
<gadget id="calculator">12 * 30</gadget>
<output>360</output>

<gadget id="calculator">12 + 6</gadget>
<output>18</output>

<gadget id="calculator">360 / 18</gadget>
<output>20</output>

<result>20</result>