The original 5kg of sugar is used up (1/3) for the first time, and 2kg is used up for the second time, what fraction is left?
原有5kg的糖，第一次用去(1/3)，第二次用去2kg，还剩几分之几？
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

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

<gadget id="calculator">1 - (1/3) - (2/5)</gadget>
<output>4/15 = around 0.266667</output>

<result>4/15 = around 0.266667</result>