( 1)

(2)290

(3) It is estimated that the average score of mathematics in this exam is 90.

Solution: (1) In stratified sampling, the probability of each individual being drawn is 2 points.

Therefore, the probability of students being drawn is 3 points in ....................................................................

(2) According to the meaning of the question, 4 points.

? So it is estimated that the number of people who have reached the excellent line in this middle school is … 6 points.

⑶

3-point frequency distribution histogram.

The average score of mathematics in this exam in this school.

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It is estimated that the average score of mathematics in this school is 90. ...............................................................................................................................................................