For a project, team A works for 5 days first, team B works for another 6 days, and the project can be completed (9/10); if team B works for 3 days, team A works for another 2 days, and the project can be completed (2 /5). Question: How many days will it take for teams A and B to cooperate in this project?
一项工程，甲队先做5天，乙队再做6天，共能完成工程的(9/10)；若乙队做3天，甲队再做2天，共能完成工程的(2/5)．问：这项工程甲、乙两队合作要用多少天？
<gadget id="calculator">9 / 10</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/5) * 2</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(9/10) - (4/5)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">2 * 2</gadget>
<output>4</output>

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

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

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

<gadget id="calculator">(9/10) - (1/2)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/5) / 6</gadget>
<output>1/15 = around 0.066667</output>

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

<gadget id="calculator">1 / (1/6)</gadget>
<output>6</output>

<result>6</result>