What is the average salary of 15 employees? I. Average salary of 7 clerical cadre (out of the 15 employees) employees is $ 8500. II. Average salary of 5 officer cadre (out of the 15 employees) employees is $ 10000. III. Average salary of the 3 sub-staff employees (out of the 15 employees) is $ 2500.

From above given all statements , we have
I. Average salary of 7 clerical cadre employees = $ 8500.
Sum of salary of 7 clerical cadre employees = $ 8500 x 7 = $ 60000
II. Average salary of 5 officer cadre employees = $ 10000.
Sum of salary of 5 officer cadre employees = $ 10000 x 5 = $ 50000
III. Average salary of the 3 sub-staff employees = $ 2500.
Sum of salary of 3 sub-staff employees = $ 2500 x 3 = $ 7500
Average salary of 15 employees = Sum of salary of 7 clerical cadre employees + Sum of salary of 5 officer cadre employees + Sum of salary of 3 sub-staff employees = 60000 + 50000 + 7500 = $ 117500/15 = $ 7834