(a) Consider three positive integers, x1, x2, x3, which satisfy
the inequality below: x1 +x2 +x3 =17. (1) Let’s assume each element
in the sample space (consisting of solution vectors (x1, x2, x3)
satisfying the above conditions) is equally likely to occur. For
example, we have equal chances to have (x1, x2, x3) = (1, 1, 15) or
(x1, x2, x3) = (1, 2, 14). What is the probability the events x1
+x2 ≤8occurs,i.e.,P(x1 +x2 ≤8|x1 +x2 +x3 =17andx1,x2,x3 ∈Z+)(Z+...