What percentage of the employees passed the Certification Exam from centres E, F and G out of the total number of employees enrolled from the same centre?

Out of the total Employees enrolled, E, F and G had total share of 8+12+16 = 36%
So the total number of employess enrolled from these three were, $$0.36\times\ 23550$$

Of all the employees who passed the exam, E, F, and G had a total share of 9+15+12 = 36%
So the total number of employees who passed from these three were, $$0.36\times\ 3700$$

Therefore the percentage of employees who passed from E, F and G were $$\frac{0.36\times\ 3700}{0.36\times\ 233550}\times\ 100=15.711\%$$