explain in baby steps please:

Data compiled by the Department of Justice on the number of people arrested for serious crimes (murder, forcible rape, robbery, and so on) in 1988 revealed that 89% were male and 11% were female. Of the males, 30% were under 18, whereas 27% of the females arrested were under 18.

a) What is the probability that a person arrested for a serious crime in that year was under 18?

B) If a person for a serious crime in that year is known to be under 18, what is the probability that the person is female?

THank you