A project was originally planned to be completed by 30 people in 18 days, but now it needs to be completed 3 days ahead of schedule. How many people need to be added?
一项工程，原计划30人18天完成，现在要提前3天完成，需要增加几人？
<gadget id="calculator">30 * 18</gadget>
<output>540</output>

<gadget id="calculator">18 - 3</gadget>
<output>15</output>

<gadget id="calculator">540 / 15</gadget>
<output>36</output>

<gadget id="calculator">36 - 30</gadget>
<output>6</output>

<result>6</result>