Given that the sum of two different unit fractions is (1/12), what is the minimum value of the difference between these two unit fractions (the larger fraction is the minuend).
已知两个不同的单位分数之和是(1/12)，则这两个单位分数差(较大分数为被减数)的最小值是多少．
<gadget id="calculator">4 / 84</gadget>
<output>1/21 = around 0.047619</output>

<gadget id="calculator">3 / 84</gadget>
<output>1/28 = around 0.035714</output>

<gadget id="calculator">(1/21) - (1/28)</gadget>
<output>1/84 = around 0.011905</output>

<result>1/84 = around 0.011905</result>