It takes 7 people 11 days to repair a section of road. If the task is to be completed 4 days ahead of schedule, how many people should be added?
维修一段公路，7人11天可以完成，如果；要提前4天完成任务，应该增加多少人．
<gadget id="calculator">7 * 11</gadget>
<output>77</output>

<gadget id="calculator">1 / 77</gadget>
<output>1/77 = around 0.012987</output>

<gadget id="calculator">11 - 4</gadget>
<output>7</output>

<gadget id="calculator">(1/77) * 7</gadget>
<output>1/11 = around 0.090909</output>

<gadget id="calculator">1 / (1/11)</gadget>
<output>11</output>

<gadget id="calculator">11 - 7</gadget>
<output>4</output>

<result>4</result>