Given that A:B=5:7; B:C=3:4, and the sum of A and B is 84, what is the sum of B and C?
已知甲：乙=5：7；乙：丙=3：4，而且甲、乙两数的和是84，则乙、丙两数的和是多少？
<gadget id="calculator">7 + 5</gadget>
<output>12</output>

<gadget id="calculator">7 / 12</gadget>
<output>7/12 = around 0.583333</output>

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

<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">(7/12) / (3/7)</gadget>
<output>49/36 = around 1.361111</output>

<gadget id="calculator">84 * (49/36)</gadget>
<output>343/3 = around 114.333333</output>

<result>343/3 = around 114.333333</result>