The average of four numbers is 8. If one of the numbers is changed to 2, the average of these four numbers is 5. What is the changed number?
有四个数的平均数是8，若把其中一个数改为2，则这四个数的平均数是5，改动的这个数原来是多少．
<gadget id="calculator">8 - 5</gadget>
<output>3</output>

<gadget id="calculator">3 * 4</gadget>
<output>12</output>

<gadget id="calculator">12 + 2</gadget>
<output>14</output>

<result>14</result>