A class of 43 students took an exam. Their mean grade average is 67 and standard deviation is 7.

Question

a) how many students should get a C?
b) how many should get a B?
c) what score is necessary to get an A?

Answer 1

Here is an excellent applet that will do these kind of questions.

http://davidmlane.com/hyperstat/z_table.html

Unless I know what is considered a C in your country or region, I can't finish the problem for you

enter the mean, the standard deviation, then choose the "between" option
Enter the low end and the high end of your letter grade range.

Answer 2

(pushed the post button too early)

the result you get will be a decimal between 0 and 1, the probability.

multiply that by the number of students, the 43