Xiaohong reads a story book, reads (1/2) on the first day, reads 20% on the second day, how much is left.
小红看一本故事书，第一天看了(1/2)，第二天看了20%，还剩多少没有看．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/2) - (1/5)</gadget>
<output>3/10 = around 0.3</output>

<result>3/10 = around 0.3</result>