Li Ming can read a storybook in 15 days, but Zhang Wei takes 2 days more than Li Ming, and Li Ming reads 4 more pages than Zhang Wei every day. How many pages does this story book have?
一本故事书，李明15天可以看完，而张伟比李明多用2天，李明每天比张伟多看4页．这本故事书共有多少页．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">15 * 2</gadget>
<output>30</output>

<gadget id="calculator">15 + 2</gadget>
<output>17</output>

<gadget id="calculator">30 * 17</gadget>
<output>510</output>

<result>510</result>