A glass of milk, the elder brother drank (1/4), the younger brother drank (2/4), what fraction of this glass of milk is left undrinked?
一杯牛奶，哥哥喝了(1/4)，弟弟喝了(2/4)，这杯牛奶还剩几分之几没有喝？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">2 / 4</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (1/4) - (1/2)</gadget>
<output>1/4 = around 0.25</output>

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