The statement of the problem is faulty and/or incomplete.
With the problem as stated, one can only guess what the question was supposed to be....
Note that the average of any number of fours is 4; so the average of two thousand fours is 4.
Perhaps the question is supposed to say "the average of 2000 fours equals the average of 1000 of what number", in which case the answer is of course 4.
