A book, after reading it (1/3) is 30 pages less than after reading it (2/5), how many pages is this book in total?
一本书，读完它的(1/3)比读完它的(2/5)少30页，这本书一共多少页．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

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

<gadget id="calculator">(2/5) - (1/3)</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">30 / (1/15)</gadget>
<output>450</output>

<result>450</result>