To complete a task, Master Li alone takes 20 hours, and Master Wang alone takes 30 hours. Now the two are working together, Master Li asks for 5 hours off halfway, how many hours did he spend in completing the task?
完成一项任务，李师傅独做要20小时，王师傅独做要30小时．现在两人合做，李师傅中途请假5小时，完成任务时一共用了多少小时．
<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/30) * 5</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">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/20) + (1/30)</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(5/6) / (1/12)</gadget>
<output>10</output>

<gadget id="calculator">10 + 5</gadget>
<output>15</output>

<result>15</result>