The average of 5 numbers is 30. Arrange them in a row. The average of the first 3 numbers is 25, and the average of the last 3 numbers is 35. What is the middle number?
5个数的平均数是30，把它们排成一列，前3个数的平均数是25，后3个数的平均数是35，中间的数是多少？
<gadget id="calculator">25 * 3</gadget>
<output>75</output>

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

<gadget id="calculator">75 + 105</gadget>
<output>180</output>

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

<gadget id="calculator">180 - 150</gadget>
<output>30</output>

<result>30</result>