At one college, 2/3 of the professors have doctorates. If a student signs up for 5 classes, what is the probability that 4 of the professors will have a doctorate?

I have difficulty defining the X in the binomial distribution?????

If you use a binomial probability table, x = 4, p = 2/3 (convert to a decimal), and n = 5. Check the table for your probability.