Probability change

Suppose i have a set [A,B,C]
Probability of A =10% B=40% C=50%
If probability of C lowers to 25%, how the remainder value is distributed(proportionaly)?
I know it suppose to get like 15(+50%),60(+50%),25 but what if the set grows?
exmaple       5,77,3,15(-5) becomes 6.65,102,4,10
I'm looking for a formula for arbitrary sets of probability(not just 3).

What drives a man to study statistics?
Fear of determinism?
The desire for anarchy and hatred of the illuminati?
The belief that humans are in essence statistics machines and that they can only be emulated using our inherently rational and probabilistic artificial intelligence techniques?
Or simply so they can sound smart on the internet?