project can be completed by team A in 15 days, and by team B in 10 days. Now, after a few days, team A will take over from team B to complete the remaining tasks. It is known that team A will do the rest of the work B spent 3 extra days, how many days did B work alone? (column solution)
一项工程，甲队独做要15天完成，乙队独做要10天完成，现在先由乙单独独做若干天后，甲队接替乙队完成余下的任务，已知甲做余下的工作比乙多用了3天，乙单独工作了多少天？(列式解答)
<gadget id="calculator">3 / 15</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

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

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/10) + (1/15)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(4/5) / (1/6)</gadget>
<output>24/5 = around 4.8</output>

<result>24/5 = around 4.8</result>