Xiao Ming reads a book and has already read (1/5) of the whole book. If he reads 15 more pages, the ratio of the number of pages he has read to the number of pages he has not read is 2:3. How many pages does this book have?
小明读一本书，已经读了全书的(1/5)，如果再读15页，则读过的页数与未读的页数的比是2：3，这本书有多少页？
<gadget id="calculator">2 + 3</gadget>
<output>5</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(2/5) - (1/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">15 / (1/5)</gadget>
<output>75</output>

<result>75</result>