equations

good question refer ca_cpt books  

I got the answer, but i am not able to know the method how the answer came

let the present age of grandsons be x each.
so the present age = 8 + 3(2x) i.e (8+6x)
after 8 years.
8+6x+8 = 10+2[(x+8)2]
16+6x = 10+2[2x+16]
solving the above equation x=13.

So the present age of man =8+6x i.e. 86 Years
present age of grandsons =x=13.

so when grandsons were born age of man = 86-13 = 73 Years.

73 is the answer.

6X+8=age of man

6X+16=4X+32+10
X=13=grandson age

Age of man = 86

Age at the time of born of grandsons =86-13=73