Two masters and apprentices complete a task, the master completes it within 10 days, the apprentice can complete this task in 5 days (1/3), and the master and apprentice cooperate to complete this task (2/3), how many days will it take?
师徒二人完成一项任务，师傅10天内完成，徒弟5天能完成这项任务的(1/3)，师徒合作完成这项任务的(2/3)，需要几天？
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

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

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

<gadget id="calculator">(1/10) + (1/15)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(2/3) / (1/6)</gadget>
<output>4</output>

<result>4</result>