To print a manuscript, it takes 12 hours for A to print alone, and 15 hours for B to print alone. After two hours of working together, the rest will be printed by A alone. How many hours will it take to complete?
打印一份稿件，甲单独打印要12小时，乙单独打印要15小时．两人合打2小时后，剩下的由甲单独打印，还要几小时完成？
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/12) + (1/15)</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">(3/20) * 2</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (3/10)</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">(7/10) / (1/12)</gadget>
<output>42/5 = around 8.4</output>

<result>42/5 = around 8.4</result>