The average of the two numbers A and B is 16, and the average of the three numbers A, B, and C is 20. You can calculate the number of C.
甲、乙两数的平均数是16，甲、乙、丙三数平均数是20，可算出丙数为多少．
<gadget id="calculator">20 * 3</gadget>
<output>60</output>

<gadget id="calculator">16 * 2</gadget>
<output>32</output>

<gadget id="calculator">60 - 32</gadget>
<output>28</output>

<result>28</result>