The probability a girl wears spectacles is 1/12 and the probability a student who wears spectacles is a girl is 1/9 . The probability that a student selected randomly is not a girl and does not wear spectacles is 3/4 . What is the probability that another person chosen randomly is a girl who wears spectacles ?
Let S=spectacles and G=girl
P(G n S)=1/12
P(G' n S')=3/4
and the question is asking for P(G n S) again ??