If two people are of the same type,then they are either both knights or both liars.
If they are of different types,then one is a knight and one is a liar.
Now, suppose Drew and Mohammad say the following.
Drew: We are of the same type.
Mohammad: We are of different types.
Now, what are each?
As Drew and Mohammad say different things, they are of different types, so Mohammad is a knight and Drew a liar ...