For a project, team A will complete it in 12 days alone, and team B will complete it in 15 days. Team A will work on it for 3 days first, and then team B will join in. How many days will it take to complete the task?
一项工程，甲队单独做要12天完成，乙队单独做要15天完成，甲队先做3天后，乙队也加入一同做，还要多少天可以完成任务？
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(1/12) * 3</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</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">(3/4) / (3/20)</gadget>
<output>5</output>

<result>5</result>