Two engineering teams complete a project. Team A can complete it in 3 days (2/5). Teams A and B cooperate for 3 days first, and team B will complete the rest in 6 days alone. If Team A and Team B work together, how many days can the entire project be completed?
两个工程队完成一项工程，甲队3天可以完成(2/5)，甲、乙两队先合作3天，剩下的由乙队独做了6天才完成．如果甲、乙两队合作，多少天可以完成全部工程？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/5) / 3</gadget>
<output>2/15 = around 0.133333</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(3/5) / 9</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(2/15) + (1/15)</gadget>
<output>1/5 = around 0.2</output>

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

<result>5</result>