The average of the three numbers A, B, and C is (63/4), and the average of the two numbers B and C is (169/16). What is the number of A?
甲、乙、丙三数的平均数是(63/4)，乙、丙两数的平均数是(169/16)，甲数是多少．
<gadget id="calculator">63 / 4</gadget>
<output>63/4 = around 15.75</output>

<gadget id="calculator">(63/4) * 3</gadget>
<output>189/4 = around 47.25</output>

<gadget id="calculator">169 / 16</gadget>
<output>169/16 = around 10.5625</output>

<gadget id="calculator">(169/16) * 2</gadget>
<output>169/8 = around 21.125</output>

<gadget id="calculator">(189/4) - (169/8)</gadget>
<output>209/8 = around 26.125</output>

<result>209/8 = around 26.125</result>