The average of six natural numbers is 7, the average of the first four numbers is 8, and the fourth number is 11, what is the average of the last three numbers?
六个自然数的平均数是7，其中前四个数的平均数是8，第4个数是11，那么后三个数的平均数是多少．
<gadget id="calculator">7 * 6</gadget>
<output>42</output>

<gadget id="calculator">8 * 4</gadget>
<output>32</output>

<gadget id="calculator">42 - 32</gadget>
<output>10</output>

<gadget id="calculator">11 + 10</gadget>
<output>21</output>

<gadget id="calculator">21 / 3</gadget>
<output>7</output>

<result>7</result>