A watermelon, Xiao Ming ate (1/5), Xiao Hong ate (2/5), how much is left?
一个西瓜，小明吃了(1/5)，小红吃了(2/5)，还剩几分之几？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

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

<gadget id="calculator">1 - (1/5) - (2/5)</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>