A project can be completed in 5 days alone (5/7), how many days will it take for A to complete the project alone?
一项工程，甲单独做5天能完成这项工作的(5/7)，甲单独完成这项工程需要多少天．
<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">(5/7) / 5</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">1 / (1/7)</gadget>
<output>7</output>

<result>7</result>