Xiao Ming reads a book and has read (1/5) of the whole book, and there are 120 pages left. How many pages does this book have?
小明看一本书，已看了全书的(1/5)，还剩120页，这本书共有多少页？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">120 / (4/5)</gadget>
<output>150</output>

<result>150</result>