For a project, it takes 10 days for A to do it alone, and 15 days for B to do it alone. If two people cooperate, their work efficiency will decrease. A can only complete the original (4/5), and B can only complete the original ( 9/10), they need 8 days to complete the project, and the number of days for the two to work together is as few as possible, so how many days do they need to work together?
一项工程，甲独做需10天，乙独做需15天，如果两人合作，他们的工作效率就要降低，甲只能完成原来的(4/5)，乙只能完成原来的(9/10)，他们要8天完成这项工程，两人合作天数尽可能少，那么两人要合作多少天？
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/10) * 8</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">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(1/10) * (4/5)</gadget>
<output>2/25 = around 0.08</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">9 / 10</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">(1/15) * (9/10)</gadget>
<output>3/50 = around 0.06</output>

<gadget id="calculator">(3/50) - (1/10)</gadget>
<output>-1/25 = around -0.04</output>

<gadget id="calculator">(2/25) + (-1/25)</gadget>
<output>1/25 = around 0.04</output>

<gadget id="calculator">(1/5) / (1/25)</gadget>
<output>5</output>

<result>5</result>