Posted by PRIDE on .
The positive integer 4 can be represented as a sum of 1's or 2's in
five ways, such as 1 + 2 + 1 and 1 + 1 + 2. Show all the ways that
the positive integer 5 can be represented as a sum of 1's or 2's.

algebra 
drwls,
1 + 2 + 2
2 + 1 + 2
2 + 2 + 1
1 + 1 + 3
1 + 3 + 1
3 + 1 + 1