A project can be completed in 10 days alone, B can be completed in 12 days alone, C can be completed in 15 days alone, after three people work together for a certain number of days, A changes to other projects, and B and C continue to work on the rest 5 days to complete, how many days did this project A do?
一项工程，甲单独做10天可完成，乙单独做12天可完成，丙单独做15天可完成，三人合做若干天后，甲改做其他工程，剩下部分由乙、丙继续工作5天完成，这项工程甲做了多少天？
<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) * 5</gadget>
<output>3/4 = around 0.75</output>

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

<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/10) + (1/12) + (1/15)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/4) / (1/4)</gadget>
<output>1</output>

<result>1</result>