The average of five numbers is 12. If one of the numbers is changed to 18, the average becomes 10. What is the original number.
五个数的平均数是12，如果把其中一个数改成18后，平均数就变成了10．原来这个数是多少．
<gadget id="calculator">12 * 5</gadget>
<output>60</output>

<gadget id="calculator">10 * 5</gadget>
<output>50</output>

<gadget id="calculator">60 - 50</gadget>
<output>10</output>

<gadget id="calculator">10 + 18</gadget>
<output>28</output>

<result>28</result>