It is known that the average of three numbers is 84, and one of the numbers is 24, which is twice the other number, so what is the third number.
已知三个数的平均数是84，其中一个数是24，是另一个数的2倍，那么，第三个数是多少．
<gadget id="calculator">84 * 3</gadget>
<output>252</output>

<gadget id="calculator">24 / 2</gadget>
<output>12</output>

<gadget id="calculator">252 - 24 - 12</gadget>
<output>216</output>

<result>216</result>