Lang Lang read (4/5) of a story book, and there are 16 pages left. How many pages does this book have?
朗朗看了一本故事书的(4/5)，还剩16页没看，这本书一共有多少页？
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">16 / (1/5)</gadget>
<output>80</output>

<result>80</result>