The seven numbers whose average number is 29 are arranged in ascending order. The average number of the first four numbers is 23, and the average number of the last four numbers is 35. What is the middle number?
平均数是29的七个数从小到大排列，前四个数的平均数是23，后四个数的平均数是35，那么中间那个数是多少．
<gadget id="calculator">23 * 4</gadget>
<output>92</output>

<gadget id="calculator">35 * 4</gadget>
<output>140</output>

<gadget id="calculator">29 * 7</gadget>
<output>203</output>

<gadget id="calculator">140 - 203</gadget>
<output>-63</output>

<gadget id="calculator">92 + (-63)</gadget>
<output>29</output>

<result>29</result>