project is completed in 10 days alone, and B is completed in 8 days alone. How many days will it take for the two teams to complete the project (4/5)? Please list the formula for directly calculating the number of cooperation days.
一项工程甲单独做10天完成，乙单独做8天完成，两队完成这项工程的(4/5)要多少天？请列出直接计算合作天数的式子是多少．
<gadget id="calculator">4 / 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 / 8</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">(1/10) + (1/8)</gadget>
<output>9/40 = around 0.225</output>

<gadget id="calculator">(4/5) / (9/40)</gadget>
<output>32/9 = around 3.555556</output>

<result>32/9 = around 3.555556</result>