I don't agree with their answer . . .
How many solutions are there to:
. . . for integers
The answer has been given as 130,905.
Consider a 50-inch dowel ... marked in one-inch intervals.
There are 49 marks along the dowel.
We will select 4 of them to make our cuts, dividing the dowel into 5 parts.
There are: . choices.
Therefore, there are 211,876 solutions.