Call x Andrew's age.
Then, Carol is 3 times older => Carol's age is 3x
And, Brad is 2 year older than Andrew => Brad's ages x + 2
In six years, Carol's age will be 3x + 6, Brad's age will be x + 2 + 6 and Andrew's age will be x + 6
Then, the sum of Andrew's and Brad's ages in six years will be:
(x + 6)+ (x + 2 + 6) = 3x + 6
Now, you can solve the equation:
x + 6 + x + 8 = 3x + 6
=> 3x - x - x = 8
=> x = 8.
So, today Carol's age = 3x = 3(8) = 24.
Answer: 24 years