The solution for this problem is:
One way to solve is to using the "stars and bars"
approach, but this could be the other one:
x1 + x2 + x3 + x4 + x5 + x6 + x7 + x8 + x9 + x10 = 20
then use (20+10-1) C(10-1), this will
result to 29C9.
Then find the way to distribute x
as a result, (20-10+10-1) C (10-1) = 19C9
Thus, the probability is 19C9/29C9 or 0.0093
