A project can be completed in 6 hours if A and B work together. Now they work together to complete the task. A stops work for 2.5 hours in the middle, so it takes 7.5 hours to complete the project. How many hours would it take for the project to be completed by A alone?
一项工程，甲、乙合做6小时可以完成，现两人一起来完成任务，中途甲停工了2.5小时，这样共经过7.5小时完工．如果这项工程由甲单独完成要多少小时？
<gadget id="calculator">6 / 3</gadget>
<output>2</output>

<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<gadget id="calculator">4 + 6</gadget>
<output>10</output>

<result>10</result>