For part 1, you are told that your sample space consists of the top 75% of all Tweeters, which is 0.10 of total Tweeters. We also know, that of this proportion of Tweeters, 0.30 of them are actually Bots (there may be bots elsewhere, but we're not concerned with that). So of all Tweeters, 0.03 of them are bots and in the top 75% of Tweeters. Thus the probability of an actual user would be the compliment to the probability that it is a bot given it's in the Top 75%:
For Part 2, an account belonging to a male, and it being empty are not independent events. Are you comfortable with the idea of "If. . .given" statements to determine sample space (which is all a "given" statement is - a reevaluation of the initial sample space, which in this case is ALL of Twitter Accounts).