If a single letter is drawn from the set {m, a, t, h, e, i, c, s}

what is the probability that the letter drawn is a member
of the set
{m, a, t, h}?

What is the cardinality (number of members), N1, of the set of possible outcomes?

What is the cardinality, N2, of the set of successful candidates?
The probability is N2/N1.