Seven years ago, Grogg's dad was $9$ times as old as Grogg. Four years ago, Grogg's dad was $6$ times as old as Grogg. How old is Grogg's dad currently?
9 ( G - 7) = D - 7 → 9G - 63 = D - 7 → 9G = D + 56 (1)
6 ( G - 4) = D - 4 → 6G - 24 = D - 4 → 6G = D + 20 (2)
Multiply (2) by 1.5
9G = 1.5D + 30 (3)
Set ( 1) = (3)
1.5D + 30 = D + 56
.5D = 26
(1/2)D = 26 mult both sides by 2
D = 52
+866 
