In a story book, the ratio of the number of pages that Xiao Ming has read to the number of pages he has not read is 2:3. Read 45 more pages and finish reading. How many pages are there in this book?
一本故事书，小明已读的与未读的页数之比为2：3．再读45页就读完了，这本书共有多少页？
<gadget id="calculator">2 + 3</gadget>
<output>5</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">45 / (3/5)</gadget>
<output>75</output>

<result>75</result>