It seems to me, based on the set up that there are more variables here. It doesn't say that George knows ONLY three people. So it could be anybody that equals 2450.

Variables:
a,b,c (with c being the oldest) = people known
g = George
f = Frank

a*b*c = 2450
a+b+c = 2f
c < g

Do we not know the ages of George and Frank?

WORKING BACKWARDS:
If you take 2450 and break it down into its factors, you get: 2, 5, 5, 7, 7.

That means the ages have to be one of the following combinations:

2, 25, 49
5, 10, 49
5, 14, 35
7, 10, 35
7, 14, 25
(2,35,35 won't work because "c" is the oldest so you'd need an oldest).

Maybe, by knowing the possible answers, you can work backwards. Hope this helps.