Xiaoli reads a book and plans to read the whole book every day (2/7). After 3 days of reading, there are 280 pages left. How many pages does this book have?
小丽读一本书，计划每天读全书的(2/7)，读了3天后，还剩280页没有读，这本书共有多少页？
<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">(2/7) * 3</gadget>
<output>6/7 = around 0.857143</output>

<gadget id="calculator">1 - (6/7)</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">280 / (1/7)</gadget>
<output>1_960</output>

<result>1_960</result>