P(S∪T)=34
Explanation:We use the following fundamental definition from Probability and Set Theory:
P(A∪B)=P(A)+P(B)−P(A∩B)
And if we apply this to our problem we have:
P(S∪T)=P(S)+P(T)−P(S∩T)
=13+512−P(S∩T)
=34−P(S∩T)
Now we are told that S and T are mutually exclusive, and so:
P(S∩T)=0
Hence,
P(S∪T)=34
