There is a batch of books that Xiaoming can bind in 9 days (3/4), and Xiaoli can bind in 20 days (5/6). If Xiaoming and Xiaoli work together, how many days can the installation be completed?
有一批书，小明9天可装订(3/4)，小丽20天可装订(5/6)．如果由小明和小丽两人合作，那么多少天可以装完．
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">(3/4) / 9</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">5 / 6</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">(5/6) / 20</gadget>
<output>1/24 = around 0.041667</output>

<gadget id="calculator">(1/12) + (1/24)</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">1 / (1/8)</gadget>
<output>8</output>

<result>8</result>