job alone takes 12 hours to complete. After A and B cooperated for 2 hours, A went out due to business, and it took B another 5.5 hours to finish the remaining work. How many hours would it take if the job was done by B alone?
一件工作，甲单独做需要12小时完成．现甲、乙合作2小时后，甲因事外出，剩下的工作乙又用了5.5小时才做完．如果这件工作由乙单独完成，需要几小时？
<gadget id="calculator">2 + 5.5</gadget>
<output>7.5</output>

<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">2 * (1/12)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 - (1/6)</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">7.5 / (5/6)</gadget>
<output>9</output>

<result>9</result>