First, I am not a teacher, but I am a native speaker.
I know that people have a hard time with subject/verb agreement and the "X of the Y" formation often has people matching the verb to Y instead of X, but any time I see a rule that says "never" I am doubtful.
What do you think about "Twelve of the students voted for a pizza party and ten voted for hamburgers."
I think the subject has to be "twelve of the students" and that "ten" is just an abbreviated version of "ten of the students."
However, I'm sure a proper teacher will come in to clera the doubts.
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