The number A is (6/7) the average of the two numbers B and C, and the number A is ((())/(())) the average of the three numbers A, B, and C.
数A是B、C两数平均数的(6/7)，数A是A、B、C三数的平均数的((())/(()))．
<gadget id="calculator">6 / 7</gadget>
<output>6/7 = around 0.857143</output>

<gadget id="calculator">20 / 21</gadget>
<output>20/21 = around 0.952381</output>

<gadget id="calculator">(6/7) / (20/21)</gadget>
<output>9/10 = around 0.9</output>

<result>9/10 = around 0.9</result>