It takes A alone 20 days and B alone 30 days to complete a project. Now the two of them work together, and it is known that A took 3 days of personal leave during work, and then went on a business trip for 2 days. How many days did it take them to complete the project from start to finish?
完成某一项工程，甲单独干需要20天，乙单独干需要30天．现在由他们两人合干，又知甲在工作途中先请了3天事假，后因公事出差2天．他们完成这项工程从开工到结束一共多少天？
<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

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

<gadget id="calculator">(1/20) * 2</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(3/20) + (1/10) + 1</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/20) + (1/30)</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(5/4) / (1/12)</gadget>
<output>15</output>

<result>15</result>