The average of three numbers is 20.5, the first number is 15.5, the second number is 1.5 times the first number, what is the third number?
三个数的平均数是20.5，第一个数是15.5，第二个数是第一个数的1.5倍，第三个数是多少？
<gadget id="calculator">20.5 * 3</gadget>
<output>61.5</output>

<gadget id="calculator">15.5 * 1.5</gadget>
<output>23.25</output>

<gadget id="calculator">61.5 - 15.5 - 23.25</gadget>
<output>22.75</output>

<result>22.75</result>