The master and the apprentice process a batch of parts. The master works for 2 days, and the apprentice works for 4 days. After completing (1/3) of the processing task, the master and the apprentice work together for 5 days. Completed all processing tasks. Ask the apprentice to complete the processing task of this batch of parts, how many days will it take?
师傅和徒弟加工一批零件，师傅工作2天，接着徒弟工作4天后，做完加工任务的(1/3)，最后师傅和徒弟共同工作了5天．完成了全部加工任务．问这批零件的加工任务由徒弟一人来完成，需要多少天？
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 - (1/3)</gadget>
<output>2/3 = around 0.666667</output>

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

<gadget id="calculator">(2/15) * 2</gadget>
<output>4/15 = around 0.266667</output>

<gadget id="calculator">(1/3) - (4/15)</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">4 - 2</gadget>
<output>2</output>

<gadget id="calculator">(1/15) / 2</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">1 / (1/30)</gadget>
<output>30</output>

<result>30</result>