The average of the numbers A, B, and C is 8.6, and the average of the two numbers of A and B is 11. What is the number of C?
甲、乙、丙三数的平均数为8.6，甲乙两数平均数为11，则丙数是多少．
<gadget id="calculator">8.6 * 3</gadget>
<output>25.8</output>

<gadget id="calculator">11 * 2</gadget>
<output>22</output>

<gadget id="calculator">25.8 - 22</gadget>
<output>3.8</output>

<result>3.8</result>