Problem: 
Stephen read 100
pages of his book. He skipped 20 pages. How many more pages
does he have to read to finish the book? 

Fact 
Question 
Read 
He read 100 pages.
He skipped 20 pages. 
How many more pages does he
have left to read? 
Plan 
To find the number of pages
left, subtract. 
This problem can
not be solved.
There is information missing. 
Missing
Information 
The number of
total book pages. 
The missing information must be
supplied in order to solve this problem. 
Solve 
As stated, this
problem can not
be solved. There is missing information. 