Learn Spanish (Latin America): La mayoría de las casas pertenecen al banco.

This is a special type of agreement often called "agreement by sense." When a singular group word (like la mayoría or un grupo) is connected to a plural noun (las casas) with de, the verb can be singular or plural! Both pertenece (agreeing with the singular mayoría) and pertenecen (agreeing with the plural casas) are completely correct. Using the plural is very common in everyday Spanish.

If we already know we are talking about houses, can I just say La mayoría pertenecen al banco?

Yes! You can drop de las casas if it is obvious from the context. What is really useful to know is that even when you drop the plural noun from the sentence, you can still use the plural verb (pertenecen) because the plural "houses" is still the understood meaning in your head.

If I just wanted to say "Most houses" (instead of "Most of the houses"), would I drop the las?

No, you should still keep it! While English distinguishes between "most houses" (general) and "most of the houses" (specific), Spanish almost always translates both as la mayoría de las casas. Dropping the las and saying la mayoría de casas sounds unnatural to most native speakers.

Why do we use al before banco?