pr.probability – Probability help – MathOverflow

This might sound like a dumb question, but I completely forgot how probability works

Say there is a city where 30% of the population has a trait A. From those 30% who has the trait, 90% of them also have a trait B, while 30% of the rest of the population only has the trait B

If I were to pick someone randomly, what would be the probability of that person having both A and B