Read a book, read the whole book (2/5) in the first week, read more (1/10) of the whole book in the second week than the first week, and not read the whole book.
读一本书，第一周读了全书的(2/5)，第二周比第一周多读了全书的(1/10)，没有读的是全书的多少．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(2/5) + (1/10)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (2/5) - (1/2)</gadget>
<output>1/10 = around 0.1</output>

<result>1/10 = around 0.1</result>