Wang Fang read a book, originally planned to finish it in 10 days, but actually read the whole book 2 days before (2/5). According to this progress, how many days in advance can I watch it?
王芳看一本书，原计划10天看完，实际前2天就看了全书的(2/5)．照这样的进度，可以提前几天看完？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">2 / (2/5)</gadget>
<output>5</output>

<gadget id="calculator">10 - 5</gadget>
<output>5</output>

<result>5</result>