A project can be completed by A alone in 12 hours, and B can only complete (4/5) of the project in the same time. How many hours can B alone complete the whole project?
一项工程，甲单独做12小时完成，乙在相同时间里只能完成这项工程的(4/5)，乙单独做多少小时完成全工程．
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">12 / (4/5)</gadget>
<output>15</output>

<result>15</result>