project is completed in 20 days jointly by A and B. After A and B have worked together for 8 days, the rest will be completed by A alone in 30 days. How many days will it take if the rest is done by B alone?
一项工程甲乙合做20天完成，甲乙两人先做了8天后，剩下的由甲单独做要30天完．如果剩下的由乙单独做要多少天完成？
<gadget id="calculator">8 / 20</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(3/5) / 30</gadget>
<output>1/50 = around 0.02</output>

<gadget id="calculator">(1/20) - (1/50)</gadget>
<output>3/100 = around 0.03</output>

<gadget id="calculator">(3/5) / (3/100)</gadget>
<output>20</output>

<result>20</result>