The factory needs to complete a batch of parts, 120 parts per day, which can be completed in 20 days. If 150 are completed every day, how many days can it be completed in advance?
工厂要完成一批零件，每天完成120个，20天可以完成．如果每天完成150个，能够提前几天完成？
<gadget id="calculator">20 / 150</gadget>
<output>2/15 = around 0.133333</output>

<gadget id="calculator">120 * (2/15)</gadget>
<output>16</output>

<gadget id="calculator">20 - 16</gadget>
<output>4</output>

<result>4</result>