If a piece of work is done alone, A can finish it 3 days earlier than the stipulated time, and B will finish it 3 days ahead of the stipulated time. If A and B work together, how many days will it take to complete this task?
一件工作，如果单独做，甲可比规定时间提前3天完成，乙则要超过规定时间3天完成，现在甲、乙两人合做2天后，剩下的继续由乙单独做，刚好在规定的日期内完成，若甲、乙二人合做，则完成这件工作需多少天．
<gadget id="calculator">6 + 9</gadget>
<output>15</output>

<result>15</result>