We know that we have five vowels in the alphabet. Since the deck has uppercase and lower case cards this means that it has a total of 10 vowels.
The probability is given by the quotient between the number of favorable outcomes and the number of total outcomes; then in this case we have:
[tex]P=\frac{10}{52}=\frac{5}{26}[/tex]Therefore the probability of selecting a vowel is 5/26
