The average of three numbers is 18, two of which are 10 and 24 respectively, what is the third number
三个数的平均数是18，其中两个数分别是10、24，第三个数是多少
<gadget id="calculator">18 * 3</gadget>
<output>54</output>

<gadget id="calculator">54 - 10 - 24</gadget>
<output>20</output>

<result>20</result>