To answer this question we will use the theoretical probability that an event occurs:
[tex]\frac{favorable\text{ }cases}{Total\text{ }cases}.[/tex]We know that there are 26 letters in the alphabet, then there are 21 letters that are not one of the five vowels.
Therefore the theoretical probability of choosing a letter that is not one of the five vowels is:
[tex]\frac{21}{26}.[/tex]Answer:
[tex]\frac{21}{26}.[/tex]