There are four numbers, choose two of them each time, calculate their sum, and then subtract the average of the other two numbers to get the following six numbers: 4, 7, 10, 16, 19, 22. What is the average of the original four numbers?
有四个数，每次选取其中两个数，算出它们的和，再减去另外两个数的平均数，共得到下面六个数：4、7、10、16、19、22．则原来四个数的平均数是多少．
<gadget id="calculator">4 + 7 + 10 + 16 + 19 + 22</gadget>
<output>78</output>

<gadget id="calculator">12 - 6</gadget>
<output>6</output>

<gadget id="calculator">78 / 6</gadget>
<output>13</output>

<result>13</result>