The average of five numbers is 30. If these five numbers are arranged in ascending order, then the average of the first three numbers is 25, and the average of the last three numbers is 35. What is the third number?
五个数的平均数是30，如果把这五个数从小到大排列，那么前三个数的平均数是25，后三个数的平均数是35，第三个数是多少．
<gadget id="calculator">25 * 3</gadget>
<output>75</output>

<gadget id="calculator">35 * 3</gadget>
<output>105</output>

<gadget id="calculator">30 * 5</gadget>
<output>150</output>

<gadget id="calculator">105 - 150</gadget>
<output>-45</output>

<gadget id="calculator">75 + (-45)</gadget>
<output>30</output>

<result>30</result>