∴ Total number of people surveyed =3÷0. 15=20 (people)

∴a= 10÷20=0.5,b=0.2×20=4,c=20-3- 10-4=3,d=3÷20=0. 15.

As shown in the figure,

(2) The number of ninth-grade students in our school who scored not less than 80 points this time is 200× (0.15+0.5) =130 (person);

(3) According to the meaning of the question, we can know that there are 1 boys in Grade A, marked as A, 2 girls marked as A 1, and 2 boys marked as d 1 girls in Grade A2 and D, respectively, marked as D, so a student is randomly selected from Grade A and D. A 1d2, A 1d, a1,A2d2, A2D * * 9 kinds, in which two students happen to be a boy and a girl, and the results are as follows: aD, A 1d 1, a/kloc-.