project, A, B cooperation 10 days to complete. Now, after A works alone for 5 days, → B continues to work for 3 days, a total of (2/5) of this project is completed. How many days will it take if factory→A does this alone?
一项工程，甲、乙合作10天完成．现在有甲单独做5天后，→乙接着做3天，一共完成了这项工程的(2/5)．如果这项工厂→甲单独做，需要多少天．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

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

<gadget id="calculator">(1/10) * 3</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(2/5) - (3/10)</gadget>
<output>1/10 = around 0.1</output>

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

<gadget id="calculator">(1/10) / 2</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">1 / (1/20)</gadget>
<output>20</output>

<result>20</result>