Use variables g for grogg and d for dad. We set up the equation d-7 = 9(g-7) and d-4 = 6(g-4).
Solving these equations, we get d = 9g-56 and d=6g-20. Set 9g-56 = 6g-20 and we can get g = 12, plug it back in into the original equation, and groggs dad is 52 years old.
