15 workers can complete a task in 7 days, and now it needs to be completed 2 days ahead of schedule. If everyone has the same work efficiency, how many more workers are needed?
15个工人7天可以完成一项任务，现要提前2天完成，如果每人工作效率一样，需要增加多少工人？
<gadget id="calculator">7 - 2</gadget>
<output>5</output>

<gadget id="calculator">7 / 5</gadget>
<output>7/5 = around 1.4</output>

<gadget id="calculator">15 * (7/5)</gadget>
<output>21</output>

<gadget id="calculator">21 - 15</gadget>
<output>6</output>

<result>6</result>