The sum of two fractions is (11/12), one of the addends is (2/5), and the other is what the addend is.
两个分数的和是(11/12)，其中一个加数是(2/5)，另一个加数是多少．
<gadget id="calculator">11 / 12</gadget>
<output>11/12 = around 0.916667</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(11/12) - (2/5)</gadget>
<output>31/60 = around 0.516667</output>

<result>31/60 = around 0.516667</result>