I need help

[zhenhao]

Suppose a social network contains a number of people, each of whom has
one of two \opinions" (e.g. a preference for Mac versus PC). Each person is
connected with a set of \friends", some of the other people in the network.
You can choose any person in the network and let them see the opinions of
their friends, and if most of the friends have the same opinion, then the chosen
person will change their opinion to the one shared by the majority of their
friends. If there's an equal split, you can choose their opinion. Assuming
the network is connected, can we always nd a sequence of people so as to
ensure that they all end up with the same opinion?

What kind of knowledge do I need to solve this problem?