In 2017:-
Let the Age of C=X
Then ,
Age of B=5X ( he is 5 times as old as C)
Age of A=5X+9 ( he is 9 years older than B)
By given conditions,
(5X+9)+5X+X=97
5X+5X+X+9=97
11X+9=97
11X=97-9=88
X=88/11=8
Therefore
A's age=5*8+9=49
B's age=5*8=40
C's age=8
In 2024:-( that is after 7 years)
A's age=49+7=56
B's age=40+7=47
C's age=8+7=15
Therefore average of A and C ages in 2024 =(56+15)/2=35.5