(2) The average score is: x = 45×0. 1+55×0. 15+65×0. 15+75×0.3+85×0.25+95×0.05 = 7 1。

(3) According to the meaning of the question, the number of people in the [80,90] score segment is: 0.25× 60 =15;

The number of people in [90, 100] section is: 0.05× 60 = 3;

Stratified sampling draws a sample with a capacity of 6 from students with 80 points or above.

∴[80, 90] Select 5 people in the score section, which are marked as A, B, C, D and E respectively; [90, 100] Extract 1 person from the fraction, and record it as m. 。

Because two people are randomly selected from the sample, and the score of 1 person is not less than 90 (points).

Then the opponent's score must be in the [80,90] score segment, so you only need to determine 1 among the five people selected in the [80,90] score segment.

We take "2 people in the sample, in which 1 person scored not less than 9(0)" as event a,

Then the basic events contained in the basic event space are: (a, b), (a, c), (a, d), (a, e), (b, c), (b, e), (c, d), (c, e), (d).

Event A contains five basic events: (a, m), (b, m), (c, m), (d, m) and (e, m).

∴ The score of 1 person is not less than 9(0 points), and the probability is p (a) = 5 15 = 13.