Two engineering teams, A and B, repair a road. Team A alone takes 12 days to complete the repair, and Team B alone takes 15 days to complete the repair. Now, after A and B jointly repair it in 3 days, how much of the road is left.
甲乙两个工程队修一条公路，甲队单独修要用12天完成，乙队单独修要用15天完成，现在甲乙合修3天后，还剩下这条路的多少．
<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">(3/20) * 3</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">1 - (9/20)</gadget>
<output>11/20 = around 0.55</output>

<result>11/20 = around 0.55</result>