A project can be completed in 6 days if A and B work together, and in 10 days if B and C work together. Now A, B, and C work together for 3 days, and the remaining B can complete it in 6 days. How many days will it take B to complete this project alone?
一项工程，甲、乙合做6天可以完成，乙、丙合做10天可以完成．现在由甲、乙、丙合做3天后，余下的乙再做6天则可以完成．乙独做这项工程要几天就可以完成？
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">6 - 3</gadget>
<output>3</output>

<gadget id="calculator">(1/6) * 3</gadget>
<output>1/2 = around 0.5</output>

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

<gadget id="calculator">(1/10) * 3</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(1/2) + (3/10)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</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 / (1/15)</gadget>
<output>15</output>

<result>15</result>