The naughty parents each ate a watermelon (1/5), what fraction is left?
淘气的爸爸妈妈各吃了一个西瓜的(1/5)，还剩几分之几？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

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

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<result>3/5 = around 0.6</result>