A project can be completed in 20 days alone, and half of the project can be completed in 15 days by B alone. After the two teams work together for 6 days, what is the remaining part of the project?
一项工程，甲独做20天完成，乙独做15天完成全工程的一半，两队合做6天后，还剩下全工程的多少．
<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">15 * 2</gadget>
<output>30</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">(1/12) * 6</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (1/2)</gadget>
<output>1/2 = around 0.5</output>

<result>1/2 = around 0.5</result>