The youngest age Freddy's grandson is 8 years.
Given that,
Now based on the above information.
The following equation should be made:
F = 8G+4
And,
F + G > 67
Eliminated the F
So,
8G + 4 + G > 67
9G > 63
G > 7
So, we can conclude that the youngest age Freddy's grandson is 8 years.
Learn more about the age here: brainly.com/question/17767243