Xiaoxiao reads an extra-curricular book. I read 25% of the total pages on the first day, and 1/3 of the total pages on the second day. I read exactly 42 pages in two days. How many pages are there in this extra-curricular book? Page?
笑笑读一本课外书，第一天读了总页数的25%，第二天读了总页数的(1/3)，两天正好读了42页，这本课外书一共有多少页？
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(1/4) + (1/3)</gadget>
<output>7/12 = around 0.583333</output>

<gadget id="calculator">42 / (7/12)</gadget>
<output>72</output>

<result>72</result>