A piece of work can be completed in 12 days jointly by A and B, and (1/5) of the whole project can be completed in 3 days by A. How many days does B work alone to complete the job?
一件工作，甲、乙合做12天完成，甲3天可以完成全工程的(1/5)．乙单独做多少天完成这件工作．
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/5) / 3</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/12) - (1/15)</gadget>
<output>1/60 = around 0.016667</output>

<gadget id="calculator">1 / (1/60)</gadget>
<output>60</output>

<result>60</result>