cartoon book, Xiao Ming read (1/5) on the first day and (3/5) on the second day, how much is left?
一本卡通书，小明第一天看了(1/5)，第二天看了(3/5)，还剩多少没看？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(1/5) + (3/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>