Can "what" be plural? [duplicate]

Solution 1:

The first example looks like an awkward confluence of What do you make of this? and What do you think of this? It's either a typo or some written form of garbled thought.

The second example is "...they are what make you fat". In that example, what is referring to they, which in turn is standing for carbs. That sentence is not incorrect, it is just conversational. People do speak that way, however it is confusing in the written form.

Now that you have added other examples: What is a pronoun. The noun for which it stands may be either singular or plural. The rule is to look for the noun, which may be unexpressed, and then to match the verb form to the noun.

What make you? as a way to say "what do you think?" is correct. The last example what make you think, the noun to which what is referring is not clear to me.

Only one of your examples was originally written. The others are transcripts, verbatim reporting of speech. What is written to be read tends to be more clear than speech.