A watermelon, mother ate (1/5), Xiaohong ate (2/7), how much is left?
一个西瓜，妈妈吃了(1/5)，小红吃了(2/7)，还剩几分之几？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">1 - (1/5) - (2/7)</gadget>
<output>18/35 = around 0.514286</output>

<result>18/35 = around 0.514286</result>