To complete a project, A alone takes 12 hours, B alone takes 8 hours, and A and B cooperate in 3 hours to complete the project.
完成一项工程，甲独做要用12小时，乙独做要用8小时，甲、乙合作3小时完成这项工程的多少．
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">(1/12) + (1/8)</gadget>
<output>5/24 = around 0.208333</output>

<gadget id="calculator">(5/24) * 3</gadget>
<output>5/8 = around 0.625</output>

<result>5/8 = around 0.625</result>