Algebra

Let G be Grogg's current age, let D be Grogg's dad's current age.

 

1. "Seven years ago, Grogg's dad was 9 times as old as Grogg":
   D - 7 = 9(G - 7). We can rearrange and rewrite to get:
   D = 9G - 56.
 

2. "Four years ago, Grogg's dad was 6 times as old as Grogg":
   D - 4 = 6(G - 4), We can rearrange and rewrite to get:
   D = 6G - 20.

 

Now we have the two equations:
1. D = 9G - 56
2. D = 6G - 20

Next, we can set the right-hand sides of Equation 1 and Equation 2 equal to each other, since we know their left hands sides are equal:
9G - 56 = 6G - 20
9G - 6G - 56 = -20,
3G = 36, 

So we have: G = 12
 

Now that we have Grogg's age, we can find his dad's age. Using the first equation:
D = 9G - 56 = 9(12) - 56
D = 52
 

Thus, Grogg's dad is currently 52 years old. 

You can check this answer with equation 2, if you'd like.