Bunuel
Students in five sections, F, G, H, J and K, of an introductory accounting course were given a final exam. What is the average test score on all the students in the five sections ?
(1) The average of the final exam scores of students in sections F, G, and H was 72.
(2) The average of the final exam scores of students in sections J and K was 78.
Let the number of students in five sections, F, G, H, J and K are f, g, h , j & k respectively .
Thus average test score on all the students in the five sections = {(avg score of F, G & H)*(f+g+h) +(avg score of J & K)*(j+k)}/(f+g+h+j+k)
For simplicity , say, (f+g+h)=x & (j+k)=y , hence above expression ={(avg score of F, G & H)x +(avg score of J & K)y}/(x+y)
(1) The average of the final exam scores of students in sections F, G, and H was 72.
Hence the expression : {72x +(avg score of J & K)y}/(x+y).... no info for x, y or (avg score of J & K).....
Thus insufficient.(2) The average of the final exam scores of students in sections J and K was 78.
Hence the expression : {(avg score of F, G & H)x +78y}/(x+y).... no info for x, y or (avg score of F, G & H).....
Thus insufficient.(1) +(2) ===> The expression becomes

72x +78y)/(x+y).....................still no info for x, y.........................
Thus insufficient.Hence I would go for
option E.