Number of boys = 30
Number of girls = 25
Therefore, the total number of students 30 + 25 = 55 = n(S)
Let X be the event of choosing a boy.
Hence, n(X) = 30
Therefore, the probability of choosing a boy, P(X) = n(X)/n(S)
P(X) = 30/55
P(X) = 6/11