There are five numbers, and their average is 7. If one of the numbers is changed to 9, the average of the five numbers is 8. What is the changed number?
有五个数，他们的平均数是7，如果把其中的一个数改为9，这样五个数的平均数是8，被改动的这个数原来是多少？
<gadget id="calculator">8 * 5</gadget>
<output>40</output>

<gadget id="calculator">7 * 5</gadget>
<output>35</output>

<gadget id="calculator">40 - 35</gadget>
<output>5</output>

<gadget id="calculator">8 + 5</gadget>
<output>13</output>

<result>13</result>