There are 20 people building a road and it is planned to be completed in 15 days. Three days after the start of construction, 5 people were selected to plant trees, and the remaining people continued to build roads. If the work efficiency of each person remains the same, how many days will it actually take to complete the road.
有20人修筑一条公路，计划15天完成．动工3天后抽出5人植树，留下的人继续修路．如果每人工作效率不变，那么修完这段公路实际用多少天．
<gadget id="calculator">20 * 15</gadget>
<output>300</output>

<gadget id="calculator">20 * 3</gadget>
<output>60</output>

<gadget id="calculator">300 - 60</gadget>
<output>240</output>

<gadget id="calculator">20 - 5</gadget>
<output>15</output>

<gadget id="calculator">240 / 15</gadget>
<output>16</output>

<gadget id="calculator">3 + 16</gadget>
<output>19</output>

<result>19</result>