There are three numbers A, B, and C. Their average is 19, and the number of B is 40% less than the number of A. If the mean of the numbers A and B is 20, what is the mean of the numbers B and C?
有甲、乙、丙三个数，它们的平均数是19，乙数比甲数少40%．若甲、乙两数的平均数是20，那么乙、丙两数的平均数是多少．
<gadget id="calculator">19 * 3</gadget>
<output>57</output>

<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 + (3/5)</gadget>
<output>8/5 = around 1.6</output>

<gadget id="calculator">2 / (8/5)</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">20 * (5/4)</gadget>
<output>25</output>

<gadget id="calculator">57 - 25</gadget>
<output>32</output>

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

<result>16</result>