A project can be completed in 20 days alone, team A and B can complete it in 12 days, how many days can team B work alone (1/5).
一项工程，甲单独做20天完成，甲乙两队合做12天完成，乙队单独做多少天完成(1/5)．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

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

<gadget id="calculator">1 / 20</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">(1/5) / (1/30)</gadget>
<output>6</output>

<result>6</result>