Xiao Ming reads (2/7) of a book in 4 days, and reads ((())/(())) of this book every day on average. How many days will Xiao Ming finish this book.
小明4天看了一本书的(2/7)，平均每天看这本书的((())/(()))，再看多少天，小明才能看完这本书．
<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">1 - (2/7)</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">(2/7) / 4</gadget>
<output>1/14 = around 0.071429</output>

<gadget id="calculator">(5/7) / (1/14)</gadget>
<output>10</output>

<result>10</result>