The average of 7 numbers arranged in a row is 9, the average of the first 4 numbers is 11, and the fourth number is 10, then what is the average of the last 4 numbers?
排成一列的7个数的平均数是9，其中前4个数的平均数是11，第4个数是10，那么后4个数的平均数是多少．
<gadget id="calculator">9 * 7</gadget>
<output>63</output>

<gadget id="calculator">11 * 4</gadget>
<output>44</output>

<gadget id="calculator">63 - 44</gadget>
<output>19</output>

<gadget id="calculator">19 + 10</gadget>
<output>29</output>

<gadget id="calculator">29 / 4</gadget>
<output>29/4 = around 7.25</output>

<result>29/4 = around 7.25</result>