For a project, two teams, A and B, can complete the whole project in 6 days. Now, team A works in 4 days, and team B works in 7 days. The whole process (2/15) is left to be done, and team B completes the whole project alone. How many days will it take.
一项工程，甲、乙两队合做6天可以完成全工程，现在甲队做4天，乙队做7天后，还剩全过程的(2/15)没做，乙队单独完成全工程需要多少天．
<gadget id="calculator">2 / 15</gadget>
<output>2/15 = around 0.133333</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/6) * 4</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 - (2/15) - (2/3)</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>