Question 722565
Solution:

Let 'x' be the common factor in the ages of Lewis and Brown.

Age of Lewis is x years
Age of Brown is 2x years

After 3 years, their ages will be (x+3) and (2x+3) respectively.

(x+3)/(2x+3) = 3/5

5x+15 = 6x+9
x = 6 years 
2x = 12 years

Age of Lewis = 6 years
Age of Brown = 12 years