The average of the five numbers is 12.5. If the five numbers are arranged in descending order, the average of the first three numbers is 13.5, and the average of the last three numbers is 11.5. Then the middle number is How many?
五个数的平均数是12.5，如果将这五个数按从大到小的顺序排列，前三个数的平均数是13.5，后三个数的平均数是11.5，那么中间的那个数是多少？
<gadget id="calculator">13.5 * 3</gadget>
<output>40.5</output>

<gadget id="calculator">11.5 * 3</gadget>
<output>34.5</output>

<gadget id="calculator">12.5 * 5</gadget>
<output>62.5</output>

<gadget id="calculator">34.5 - 62.5</gadget>
<output>-28</output>

<gadget id="calculator">40.5 + (-28)</gadget>
<output>12.5</output>

<result>12.5</result>