16 years ago,
My age = x years
My grandfather’s age = 9x years
After 8 years from the present,
9x + 16 + 8 = 3(x + 8 + 16)
$\Rightarrow$ 9x + 24 = 3x + 24 + 48
$\Rightarrow$ 9x + 24 = 3x + 72
$\Rightarrow$ 9x – 3x = 72 – 24
$\Rightarrow$ 6x = 48
$\Rightarrow$ x= 8
Required ratio 8 years ago,
= (x + 8) : (9x + 8)
= (8 + 8) : (9 × 8 + 8)
= 16 : 80 = 1 : 5