There is a batch of production tasks in a certain workshop. The original plan is to do 120 tasks per day, and it will be completed in 20 days. In fact, 40 more tasks will be done per day than the original plan. How many days will it actually take to complete?
某车间有一批生产任务，原计划每天做120个，20天完成，实际每天比原计划多做40个，实际用多少天完成？
<gadget id="calculator">120 * 20</gadget>
<output>2_400</output>

<gadget id="calculator">120 + 40</gadget>
<output>160</output>

<gadget id="calculator">2_400 / 160</gadget>
<output>15</output>

<result>15</result>