Xiaoqiang reads a book and reads 15 pages a day. After 4 days, he speeds up his progress and reads the whole book (2/5). There are still 30 pages left. How many pages are there in this storybook?
小强看一本书，每天看15页，4天后加快进度，又看了全书的(2/5)，还剩下30页，这本故事书有多少页？
<gadget id="calculator">15 * 4</gadget>
<output>60</output>

<gadget id="calculator">60 + 30</gadget>
<output>90</output>

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

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">90 / (3/5)</gadget>
<output>150</output>

<result>150</result>