The average of 5 numbers is 9, if one of the numbers is changed to 1, then the average of these 5 numbers is 8. What is the changed number?
5个数的平均数是9，若把其中的一个数改为1，那么这5个数的平均数是8．问这个被改的数字是多少﹖
<gadget id="calculator">9 * 5</gadget>
<output>45</output>

<gadget id="calculator">8 * 5</gadget>
<output>40</output>

<gadget id="calculator">45 - 40</gadget>
<output>5</output>

<gadget id="calculator">1 + 5</gadget>
<output>6</output>

<result>6</result>