The three masters and apprentices cooperated to contract a project, which could be completed in 4 days. It is known that the number of days required for the master to work alone is equal to the number of days required for two apprentices to cooperate; and twice the number of days required for the master and B apprentice to work together is equal to the number of days required for A apprentice to complete alone. So how many days will it take apprentice B to finish the project alone?
师徒三人合作承包一项工程，4天能全部完成．已知师傅单干所需天数与两个徒弟合做所需天数相等；而师傅与乙徒弟合做所需天数的2倍与甲徒弟单独完成所需天数相等．那么乙徒弟单独做完这项工程需多少天．
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/4) / 2</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">(1/4) / 3</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(1/8) - (1/12)</gadget>
<output>1/24 = around 0.041667</output>

<gadget id="calculator">1 / (1/24)</gadget>
<output>24</output>

<result>24</result>