Xiaohua reads 84 pages in a book, and read 25% of the pages in the first 3 days. According to this calculation, how many days will it take to finish reading this book? (Use proportions to solve.)
小华看一本书共有84页，前3天看了全书页书的25%，照这样计算，看完这本书还需要多少天？(用比例解．)
<gadget id="calculator">84 * 3</gadget>
<output>252</output>

<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">84 * (1/4) * 3</gadget>
<output>63</output>

<gadget id="calculator">252 - 63</gadget>
<output>189</output>

<gadget id="calculator">84 * (1/4)</gadget>
<output>21</output>

<gadget id="calculator">189 / 21</gadget>
<output>9</output>

<result>9</result>