What is the probability of rolling a 5 or getting tails?

Your question is very vague but if we assume "rolling a 5" is rolling a five on a six sided dice then the probability of that would be 1/6 since there are 6 sides and 5 is just 1 side.

Again your question is very vague but if we assume "getting tails" means getting heads or tails on a 2 sided coin then the probability of that would be 1/2 since there are 2 sides and tails is just 1 side.