∫ The passing rate of students' math scores (Grade C and above) is 77.5%.

∴ 1 1+ 14+x 1 1+ 14+9+x=77.5%，

The solution is x=6,

The number of students selected in ∴ * * * is:11+14+6+9 = 40.

(2) As can be seen from the figure, the number of D-level students is 9.

Therefore, the central angle of the number of D-level students in the sector statistical chart is 360× 940 = 81;

(3) According to the figure, there are 1 1 person in Grade A,

Then the total number of A-level mathematics subjects in the county =2200× 1 140=605.

So the answer is: 40, 6.