2 masters and 4 apprentices can only process parts (3/10) in one day. If the master and apprentices add 6 people each, this batch of parts can be completed in one day. If this batch of parts is processed by an apprentice alone, how many days will it take to complete?
2个师傅和4个徒弟一天只能加工零件的(3/10)，如果师傅和徒弟各增加6人，由一天就能完成这批零件．如果这批零件由一个徒弟单独加工，需要多少天才能完成？
<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (3/10)</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">(7/10) / 6</gadget>
<output>7/60 = around 0.116667</output>

<gadget id="calculator">(7/60) * 2</gadget>
<output>7/30 = around 0.233333</output>

<gadget id="calculator">(3/10) - (7/30)</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>