If you have read the whole book (3/8), how much less is the number of pages you have read than the number of pages you have not read
一本书已看了全书的(3/8)，则已看的页数比未看的页数少多少
<gadget id="calculator">3 / 8</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">1 - (3/8)</gadget>
<output>5/8 = around 0.625</output>

<gadget id="calculator">(5/8) - (3/8)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/4) / (5/8)</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>