Li Li reads a storybook and has read (3/5), and there are 40 pages left. How many pages does this storybook have? (column equation solution)
李丽看一本故事书，已看了(3/5)，还剩下40页，这本故事书一共有多少页？(列方程解答)
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 - (3/5)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">40 / (2/5)</gadget>
<output>100</output>

<result>100</result>