A story book, Xiao Ming read (1/4) of this book on the first day, and read (1/5) more of this book on the second day than on the first day, how much of this book is left.
一本故事书，小明第一天看了这本书的(1/4)，第二天比第一天多看了这本书的(1/5)，还剩这本书的多少．
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

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

<gadget id="calculator">(1/4) + (1/5)</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">1 - (1/4) - (9/20)</gadget>
<output>3/10 = around 0.3</output>

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