A project alone takes 10 days and B alone takes 15 days. If two people work together, A's work efficiency will decrease by 20%, and B's work efficiency will decrease by 10%. Now it takes 8 days to complete this project, and the number of days that the two work together is as few as possible, so how many days should the two work together.
一项工程，甲独做需要10天，乙独做需要15天．如果两人合做，甲的工作效率要下降20%，乙的工作效率要降低10%．现在要8天完成这项工程，两人合做的天数尽可能少，那么两人要合做多少天．
<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">7 / 50</gadget>
<output>7/50 = around 0.14</output>

<gadget id="calculator">(7/50) - (1/10)</gadget>
<output>1/25 = around 0.04</output>

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

<result>5</result>