Question

Roshan said to his son,"I was as old as you are at present at time of your birth". If Roshan's age is 40 years now then son's present age is ?

Answer 1

let the age of son is x
at the time of his son birth roshan's age is x
now,2x=40
x=20

Answer 2

let the age of son is c
at the time of his sons birth roshan age is c
then it becomes 2c=40 then c=20