Zhang Hua reads a story book. He read the whole book in the first week (2/5), and the whole book in the second week (11/35). There are 120 pages left. How many pages does this storybook have?
张华看一本故事书，第一周看了全书的(2/5)，第二周看了全书的(11/35)，还剩120页．这本故事书一共有几页？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">11 / 35</gadget>
<output>11/35 = around 0.314286</output>

<gadget id="calculator">1 - (2/5) - (11/35)</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">120 / (2/7)</gadget>
<output>420</output>

<result>420</result>