A project can be completed by team A alone in 5 days, team B alone in 7 days, and the two teams cooperate to complete the project every day ((())/(())).
一项工程，甲队单独做5天完成，乙队单独做7天完成，两队合作每天完成这项工程的((())/(()))．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">(1/5) + (1/7)</gadget>
<output>12/35 = around 0.342857</output>

<result>12/35 = around 0.342857</result>