There are 6 numbers, the average number is 8.5, the average number of the first four numbers is 9.25, and the average number of the last three numbers is 10, what is the fourth number?
有6个数，其平均数是8.5，前四个数的平均数9.25，后三个数的平均数是10，则第四个是多少．
<gadget id="calculator">9.25 * 4</gadget>
<output>37</output>

<gadget id="calculator">10 * 3</gadget>
<output>30</output>

<gadget id="calculator">37 + 30</gadget>
<output>67</output>

<gadget id="calculator">8.5 * 6</gadget>
<output>51</output>

<gadget id="calculator">67 - 51</gadget>
<output>16</output>

<result>16</result>