Question

Find the number of positive integers that satisfy the following conditions:

* Each digit is a 1 or a 2 or a 3

* The sum of the digits is 10

Answer 1

There are 6 positive integers that satisfy the given conditions: 111, 112, 113, 122, 123, and 132.

Answer 2

1111111111
111111112
11111113
Now you have to find how many numbers there are whose digits sum to 8 or 7
and so on. You should see a pattern.