A project can be completed in 6 days by A and B working together; A can complete it in 10 days if A works alone, how many days can B work alone to complete it.
一项工程，甲、乙合作6天完成；甲独做10天完成，乙独做多少天完成．
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/6) - (1/10)</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">1 / (1/15)</gadget>
<output>15</output>

<result>15</result>