The average of three numbers is 8.4, the first number is 9.6, the second number is 1.5 times the third number, what is the third number.
三个数的平均数是8.4，其中第一个数是9.6，第二个数是第三个数的1.5倍，第三个数是多少．
<gadget id="calculator">8.4 * 3</gadget>
<output>25.2</output>

<gadget id="calculator">25.2 - 9.6</gadget>
<output>15.6</output>

<gadget id="calculator">1.5 + 1</gadget>
<output>2.5</output>

<gadget id="calculator">15.6 / 2.5</gadget>
<output>6.24</output>

<result>6.24</result>