There are 30 students in Mrs. Krzyzewski's class. None of them has a first name that begins with the letter "U" or the letter "Y." Eight of her students have first names that begin with "A," five have first names that begin with "E," two have first names that begin with "I", and three have first names that begin with "O." Based on this data, what is the probability that a randomly-selected student from Mrs. Krzyzewski's class has a first name that begins with a consonant?