A book has 120 pages, read (2/5) of the whole book on the first day, (1/4) of the whole book on the second day, and start from the page number on the third day.
一本书120页，第一天读了全书的(2/5)，第二天读了全书的(1/4)，第三天从第多少页读起．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(2/5) + (1/4)</gadget>
<output>13/20 = around 0.65</output>

<gadget id="calculator">120 * (13/20)</gadget>
<output>78</output>

<gadget id="calculator">78 + 1</gadget>
<output>79</output>

<result>79</result>