The average of the three numbers is 54. If one of the numbers is removed, the average of the remaining numbers is 45. What is the removed number?
3个数的平均数是54，若去掉其中一个数，剩下的数的平均数是45，去掉的这个数是多少．
<gadget id="calculator">54 * 3</gadget>
<output>162</output>

<gadget id="calculator">45 * 2</gadget>
<output>90</output>

<gadget id="calculator">162 - 90</gadget>
<output>72</output>

<result>72</result>