YouTube is a popular destination on the internet; let's look at how YouTube usage is distributed among age groups. According to the Pew Internet and American Life Project, about 70% of internet users...

YouTube is a popular destination on the internet; let's look at how YouTube usage is distributed among age groups. According to the Pew Internet and American Life Project, about 70% of internet users aged 18-29 have visited YouTube, along with 51% of those aged 30-49 and 26% of those 50 or older. About 30% of adult internet users are 18-29 years old, another 45% are 30-49, and the remaining 25% are 50 and over.
(a) Calculate the probability that a randomly selected internet user has used YouTube.
(b) If we randomly select a YouTube internet user, what is the probability they are aged 18-29?