A project can be completed in 6 days by cooperation between A and B, and can be completed by cooperation between B and C in 10 days. Now A, B and C cooperate for 3 days, and then B can complete the remaining 6 days. How many days will it take for B to complete the whole project alone?
一项工程，甲、乙合作6天完成，乙、丙合作10天可完成，现在先由甲、乙、丙合作3天后，余下的乙再做6天可完成．乙单独做全工程需几天完成？
<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>4/15 = around 0.266667</output>

<gadget id="calculator">(4/15) * 3</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">6 - 3</gadget>
<output>3</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>