Теория:

Study the information about general and specific references to quantity.
  
1. We always use of with these quantifiers when we put them in front of a noun or pronoun.

A lot of, a number of, a couple of, a bit of, plenty of
  
A lot of students take an exam at the end of the year.
  
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2. We can use the or my after of, when the reference is specific.

A lot of the people I know don’t eat chocolate.
  
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3. Some, any, much, many can be used without of in general references.

Some countries have their own rules.

4. When the reference is specific, use of + the or my. But none is always specific.

None of my friends is here.  Don’t use the.
 
5. We can omit of and use a quantifier on its own.

Did you buy tomatoes?- Yes, I bought a lot/lots/plenty.

6. When you use more or less, you emphasize quantity.

- More + plural nouns after some/any/a couple/hundreds/a lot/lots/many/no/plenty
- More + uncountable nouns after some/any/ a bit/a good deal/a little/lots/plenty
- Less + uncountable nouns after any, a bit, a good deal, a little, a lot, lots, much

I’d like a little less soup.
  
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There are a lot of students studying Spanish this year.
Источники:
www.ige3.unige.ch
www.zmescience.com
silk.com
L.G Alexander. Longman English Grammar practice for intermediate students- Harlow: Longman, 296p.