It takes 12 days for A and B to complete a job together. A first completes 1/5 of the job in 4 days, and B completes the rest alone. How many days will it take to complete this job?
一件工作，甲乙合作需要12天完成，甲先做了4天完成了这件工作的(1/5)，剩下的工作由乙单独完成，做完这件工作一共需要多少天？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(1/5) / 4</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/12) - (1/20)</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(4/5) / (1/30)</gadget>
<output>24</output>

<gadget id="calculator">24 + 4</gadget>
<output>28</output>

<result>28</result>