It takes 20 days for A to do a certain project alone, and 12 days for A and B to cooperate. After A works alone for 12 days, how many days will it take for B to continue to do the rest?
某项工程甲单独做需要20天，甲乙合作需要12天，甲单独做12天后，剩下的乙继续做需要几天能完成？
<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/20) * 12</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 - (3/5)</gadget>
<output>2/5 = around 0.4</output>

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

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

<gadget id="calculator">(2/5) / (1/30)</gadget>
<output>12</output>

<result>12</result>