Chen Jianxiang read a 240-page popular science book, and read a total of 60 pages in the first four days. Based on this calculation, how many days will he have to watch to finish it?
陈健翔同学看一本240页的科普书，前四天共看60页．照这样计算，他还要看多少天才能看完？
<gadget id="calculator">240 - 60</gadget>
<output>180</output>

<gadget id="calculator">60 / 4</gadget>
<output>15</output>

<gadget id="calculator">180 / 15</gadget>
<output>12</output>

<result>12</result>