Li Hua reads a book. He reads (1/5) of the whole book on the first day, and (1/3) of the whole book on the second day. At this time, there are 350 pages left. How many pages are there in this book?
李华读一本书，第一天读了全书的(1/5)，第二天读了全书的(1/3)，这时还剩350页，这本书共多少页？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

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

<gadget id="calculator">1 - (1/5) - (1/3)</gadget>
<output>7/15 = around 0.466667</output>

<gadget id="calculator">350 / (7/15)</gadget>
<output>750</output>

<result>750</result>