A project can be completed by A alone in 6 days and B alone in 12 days. Now the two are working together, and B rested for a few days due to illness on the way, so it took 4.5 days to complete the task. How many days did B rest due to illness?
一项工程，甲单独做6天完成，乙单独做12天完成．现两人合作，途中乙因病休息了几天，这样用了4.5天才完成任务．乙因病休息了几天？
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">4.5 * (1/6)</gadget>
<output>0.75</output>

<gadget id="calculator">1 - 0.75</gadget>
<output>0.25</output>

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

<gadget id="calculator">0.25 / (1/12)</gadget>
<output>3</output>

<gadget id="calculator">4.5 - 3</gadget>
<output>1.5</output>

<result>1.5</result>