In order to complete a reading assignment on time, Terry planned to read 80 pages per day. However, she read only 40 pages per day at first, leaving 1000 pages to be read during the last 6 days before the assignment was to be completed. How many days in all did Terry have to complete the assignment on time?  Choose the correct choice from the following options:
A) 18
B) 19
C) 17
D) 16
E) 15
D=80*X - according to the plan, assignment to be completed on time reading 80 pages per day for next X days. 19ut, Terry's plans changed so she read as follow:   40 pages for first Y days and 1000 pages for last 6 days, we get these equations:   40*Y+1000=80*X   X-Y=6 ---------&gt;&gt;X planned number of days, Y - actually used reading 40 pages per day and 6 leftover days used to complete a lump 1000 pages   From above we find that X=Y+6 and 40Y+1000=80Y+480 or 40Y=520 ---&gt;&gt;&gt;&gt;&gt; Y=13, hence X=19   Answer : 19
<result>B</result>
In order to complete a reading assignment on time, Terry planned to read 80 pages per day. However, she read only 40 pages per day at first, leaving 1000 pages to be read during the last 6 days before the assignment was to be completed. How many days in all did Terry have to complete the assignment on time?