It takes 12 days for A and B to complete a project together. Now after A and B work together for 4 days, the remaining A will complete in 20 days alone. How many days will it take Team B to do the project alone?
一项工程，甲乙合做要12天完成，现在甲乙合做4天后，余下的甲要独做20天完成．乙队独做这项工程需要多少天？
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(1/12) * 4</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 - (1/3)</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">(2/3) / 20</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/12) - (1/30)</gadget>
<output>1/20 = around 0.05</output>

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

<result>20</result>