Mike's teacher, leaves as homework the reading of a 200-page book. The assignment is to be completed within 30 days. Mike plans to read 10 pages a day. How many days before the deadline will Mike finish his reading?
Reading 10 pages per day, Mike finishes reading his book in 200 / 10 = 
<gadget id="calculator">200/10</gadget>
<output>20</output>
20 days.
Mike finishes reading his book 30 - 20 = 
<gadget id="calculator">30-20</gadget>
<output>10</output>
10 days before the deadline.

<result>10</result>