certain project needs to be completed alone in 12 days for A, and 15 days for B. Now, according to A’s 1 day, B’s 2 days, A’s 2 days, and B’s 1 day, how many days will it take to complete the task in turn?
某项工程要单独完成甲用12天，乙用15天，现在按甲1天，乙2天，甲2天，乙1天，轮流则完成任务共用几天？
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">2 / 15</gadget>
<output>2/15 = around 0.133333</output>

<gadget id="calculator">2 / 12</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/12) + (2/15) + (1/6) + (1/15)</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">1 / (9/20)</gadget>
<output>20/9 = around 2.222222</output>

<gadget id="calculator">(20/9) * 6</gadget>
<output>40/3 = around 13.333333</output>

<result>40/3 = around 13.333333</result>