It is known that the average of 9 numbers is 72. After removing one number, the average of the remaining numbers is 78. What is the removed number?
已知9个数的平均数是72，去掉一个数后，余下的数平均数为78，去掉的数是多少．
<gadget id="calculator">72 * 9</gadget>
<output>648</output>

<gadget id="calculator">78 * 8</gadget>
<output>624</output>

<gadget id="calculator">648 - 624</gadget>
<output>24</output>

<result>24</result>