A project is completed by team A first (1/5), and then by teams A and B. It took another 16 days to complete it. It is known that the work-efficiency ratio of teams A and B is 2:3. How many days did A work before the cooperation?
一项工程，由甲队先做(1/5)后，再由甲、乙两队合做，又做了16天才完成，已知甲、乙两队的工效比是2：3．合做前甲做了多少天？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(4/5) / 16</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">2 + 3</gadget>
<output>5</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(1/20) * (2/5)</gadget>
<output>1/50 = around 0.02</output>

<gadget id="calculator">(1/5) / (1/50)</gadget>
<output>10</output>

<result>10</result>