The ratio of the three numbers A, B, and C is 5:4:3. Given that the average of the two numbers B and C is 56, what is the number of A?
甲、乙、丙三个数的比是5：4：3，已知乙、丙两个数的平均数是56，则甲数是多少．
<gadget id="calculator">56 * 2</gadget>
<output>112</output>

<gadget id="calculator">4 + 3</gadget>
<output>7</output>

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">112 * (4/7)</gadget>
<output>64</output>

<gadget id="calculator">5 / 4</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">64 * (5/4)</gadget>
<output>80</output>

<result>80</result>