Case 1: %80 C dead first after A's 30% and B's 50%. A's survival probability here is then 80% * (3/3+3.5) = 36.9% and B is 80%-36.9%=43.1%
Case 2: %20 C survives the first round. B is then 100% dead. A's survival p here is 20%*30%=6% and C is 20%-6%=14%.
Overall, A survives 42.9%, B is 43.1% and C is 14%.
Ironic but truthful in life.