For this example question, it says give a systematic name of the following compound O. Here we have benzene and connected to it is this alkyl group. Now this alkyl group has four carbons involved, which means that it could represent butyl, isobutyl sect, butyl or turf butyl.
Here we'd say based on the way it looks, we have our connection on this carbon here which is connected to three methyl groups. This represents a tert butyl, so the name of the alkyl group would be tert butyl. Remember there's a- there and it's connected to a benzene, so we end a name with benzene.
So this would be the name of our given compound, Tert Butyl Benzene.