Xiaohong reads a 200-page book. She reads (1/4) of the whole book on the first day, and (1/5) of the whole book on the second day. On the third day, she should start reading from the page.
小红看一本200页的书，第一天看了整本书的(1/4)，第二天看了整本书的(1/5)，第三天应从第多少页开始看．
<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">200 * (9/20)</gadget>
<output>90</output>

<gadget id="calculator">90 + 1</gadget>
<output>91</output>

<result>91</result>