A project, after 5 days alone, B completes the remaining task in 15 days, if the whole project is completed by B in 30 days, how many days will it take for A to complete all the projects?
一项工程，甲独做5天后，余下的乙独做15天完成了任务，如果全部工程由乙独做30天完成，全部工程由甲独做需多少天完成？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) / 5</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 / (1/10)</gadget>
<output>10</output>

<result>10</result>