There are five numbers, the average is 9, if one of the numbers is changed to 1, then the average of these five numbers is 8. What is the original number of this change.
有五个数，平均数是9，如果把其中一个数改为1，那么这五个数的平均数为8．这个改动的数原来是多少．
<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">5 + 1</gadget>
<output>6</output>

<result>6</result>