To build a waterway, it will take 12 days for team A to do it alone, and 15 days for team B to do it alone. How many days to finish it?
建筑一条水坭路，甲队独做要12天，乙队独做要15天，乙队先独做工程的(1/10)，剩下的再由甲、乙两队合做，还要多少天修完？
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/12) + (1/15)</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">(9/10) / (3/20)</gadget>
<output>6</output>

<result>6</result>