My younger sister reads a book, and after 3 days, there are still 66 pages left. If she reads at the same speed for 4 days, there will be only 2/5 of the whole book left. How many pages is this book?
妹妹看一本书，看了3天还剩66页，如果以同样的速度看4天，就剩下全书的(2/5)．这本书共多少页？
<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">(3/5) / 4</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">(3/20) * 3</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">1 - (9/20)</gadget>
<output>11/20 = around 0.55</output>

<gadget id="calculator">66 / (11/20)</gadget>
<output>120</output>

<result>120</result>