A project alone takes 15 days to complete, and B alone takes 10 days to complete. For this project, A will do it alone for 3 days, and then two teams, A and B, will cooperate. How many days will it take?
一项工程，甲单独做要15天才能完成，乙单独做需要10天才能完成．这项工程，甲先单独做3天，然后甲乙两队合作，需要几天？
<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/15) * 3</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

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

<gadget id="calculator">(1/15) + (1/10)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(4/5) / (1/6)</gadget>
<output>24/5 = around 4.8</output>

<result>24/5 = around 4.8</result>