The number of people at the intermediate level is 50 (10+22+8) = 10.

The supplementary picture is shown on the right;

(2)∫ "excellent" frequency = =0.2,

∴ "Excellent" sector central angle = 360× 0.2 = 72;

(3)∵ 1000×0.2=200,

It is estimated that there are 200 students in grade 9 in this school who can get excellent math scores.