A project can be completed by A alone in 12 days. After 3 days, Team A has another task, and the rest of the project can be completed by Team B in 15 days. How many days will it take for Team B to do this project alone?
一项工程，由甲单独做12天可以完成，甲队做了3天后，另有任务，余下的工程由乙队做15天完成，求乙队单独做这项工程要多少天？
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(1/12) * 3</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">(3/4) / 15</gadget>
<output>1/20 = around 0.05</output>

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

<result>20</result>