**3/19**

x- Isha's age now

y- Grandfathers age now

4 yrs ago --- 5*(x-4)=y-4 => y=5x-16 --->(1)

8 yrs from now ---- 3*(x+8)=y+8 => y=3x+16 --->(2)

Comparing (1) & (2) we find 5x-16=3x+16 => x=16 => y=64

Now, 7 yrs ago, x-7=9, y-7=57 ---> **(x-7)/(y-7)=9/57=3/19**