For a project, A and B cooperate to complete (1/6) of the whole project every hour. If A works for 4 hours first, and B works for another 3 hours, the remaining (2/5) of the project has not been completed. So if A does it alone, how many hours can the task be completed?
一项工程，甲乙合作每小时完成全工程的(1/6)，如果甲先做4小时，乙再做3小时，还剩工程的(2/5)没完成．那么如果甲单独做，几小时能完成任务？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/6) * 3</gadget>
<output>1/2 = around 0.5</output>

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

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

<result>10</result>