It takes 15 days for team A to repair a road alone, and 12 days for team B to repair it alone. After team A repairs 6 days first, the rest will be jointly repaired by teams A and B, and it will take a few days for teams A and B to jointly repair ?
修一条公路，甲队单独修要15天，乙队单独修要12天，甲队先修6天后，剩下的由甲、乙两队合修，甲、乙两队合修还要几天？
<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/15) * 6</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

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

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

<gadget id="calculator">(3/5) / (3/20)</gadget>
<output>4</output>

<result>4</result>