Xiao Ming reads a story book, the ratio of the number of pages read to the total number of pages on the first day is 7:10, and he just finished reading 42 pages on the second day. How many pages does this book have?
小明读一本故事书，第一天读的页数与总页数的比是7：10，第二天读了42页正好读完．这本书有多少页？
<gadget id="calculator">7 / 10</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">1 - (7/10)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">42 / (3/10)</gadget>
<output>140</output>

<result>140</result>