It takes 15 days for A to complete a job alone, and 12 days for B to complete it alone. If A does this job alone first (2/5), and B continues to do the rest, how many days will B need?
一项工作，甲单独做需15天完成，乙单独做需12天完成，如果这项工作先由甲单独做(2/5)，剩下的由乙继续做，乙还要几天？
<gadget id="calculator">2 / 5</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 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(3/5) / (1/12)</gadget>
<output>36/5 = around 7.2</output>

<result>36/5 = around 7.2</result>