project needs 10 days to complete alone, and B completes (1/3) of the whole project in 10 days. A works alone for 2 days, A and B cooperate for 5 days, and B alone completes the rest. How many days does it take for B? done?
一项工程，甲单独完成需10天，乙10天完成整项工程的(1/3)，甲先单独工作了2天，甲乙合作5天，剩下的由乙单独完成，问乙多少天做完？
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/10) * 2</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/10) * 5</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(1/3) / 10</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/30) * 5</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 - (1/5) - (1/2) - (1/6)</gadget>
<output>2/15 = around 0.133333</output>

<gadget id="calculator">(2/15) / (1/30)</gadget>
<output>4</output>

<result>4</result>