Xiaohong reads a 100-page book. On the first day, she reads 12 pages, and on the second day, she reads 15 pages. On the third day, she should start reading from the page number.
小红看一本100页的书，第一天看了12页，第二天看了15页，第三天她应该从第多少页开始看．
<gadget id="calculator">12 + 15</gadget>
<output>27</output>

<gadget id="calculator">27 + 1</gadget>
<output>28</output>

<result>28</result>