Additional question: In a project, the work efficiency of A and B cooperation is (1/4), and the work efficiency of B and C cooperation is (1/5). Now this project is first cooperated by A and C for 2 days, and the remaining B works alone for 6 days Complete, how many days will it take B to complete the whole project alone?
附加题：一项工程，甲乙合作的工效是(1/4)，乙丙合作的工效是(1/5)，现在这项工程先由甲丙合作2天后，剩下的乙单独做6天完成，问乙单独完成全部工程要多少天？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/4) * 2</gadget>
<output>1/2 = around 0.5</output>

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

<gadget id="calculator">(1/5) * 2</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(1/2) + (2/5)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">1 - (9/10)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<gadget id="calculator">6 - 4</gadget>
<output>2</output>

<gadget id="calculator">(1/10) / 2</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">1 / (1/20)</gadget>
<output>20</output>

<result>20</result>