Known ((9(1/4)-7(3/5))/2(3/4))/(((1/3)+□)*1(5/7))=(21/25 ), then □=how much.
已知((9(1/4)-7(3/5))/2(3/4))/(((1/3)+□)*1(5/7))=(21/25)，那么□=多少．
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<result>1/12 = around 0.083333</result>