A project is completed in 10 days alone, and 25% of the whole project is completed in 5 days by B alone. Now B works in 8 days first, and A and B complete the remaining project together. When the project is completed, how many days did B work in total?
一项工程，甲单独做10天完成，乙单独做5天完成全工程的25%，现在乙先做8天，余下的工程甲乙共同完成，当工程完工时，乙一共做了多少天？
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/4) / 5</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/20) * 8</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 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/10) + (1/20)</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">(3/5) / (3/20)</gadget>
<output>4</output>

<gadget id="calculator">8 + 4</gadget>
<output>12</output>

<result>12</result>