If x and y are reciprocals of each other, and (4/(x))-((y)/(a)), then a=how much.
如果x与y互为倒数，且(4/(x))-((y)/(a))，那么a=多少．
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>