If the order of numbers in a sum matters, then in how many ways can you represent the number 9 as the sum of

Question

b
three positive integers?

Answer 1

Lets just look at this combo
1+2+6
1+6+2
2+1+6
2+6+1
6+1+2
6+2+1
or for that combination, six ways 3*2
Now note that you can't have a seven or 8 and get three numbers to add to nine.
1+3+5 combinations, again six ways
2+3+4 combinations, again six ways
so I count 18 ways

Answer 2

the numbers can repeat

Answer 3

If the order matters, then we can look at the following: 1+8, 2+7, 3+6, 4+5. Thats 4. Since the order matters, then we could do: 8+1, 7+2, 6+3, 5+4. The total is 8. We could also use permutations as well.

Answer 4

Actually, sorry, I read the problem wrong. There are 28 ways.