project can be completed by A alone in 6 days. If A does it on the first day, and B does it on the second day, and this is done alternately, it happens to be completed in an integer number of days. If B does it on the first day, A does it on the second day, In this way, it takes more (1/3) days to complete the rotation than the last time. How many days can A and B cooperate to complete this project?
一项工程，甲单独做6天可以完成，如果第一天甲做，第二天乙做，这样轮流交替做，恰好也用整数天完成，如果第一天乙做，第二天甲做，这样轮流交替做，比上次轮流做多(1/3)天才能完成．这项工程由甲、乙合作几天可以完成？
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(1/6) * (1/3)</gadget>
<output>1/18 = around 0.055556</output>

<gadget id="calculator">(1/6) - (1/18)</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">(1/6) + (1/9)</gadget>
<output>5/18 = around 0.277778</output>

<gadget id="calculator">1 / (5/18)</gadget>
<output>18/5 = around 3.6</output>

<result>18/5 = around 3.6</result>