You can put this solution on YOUR website! john is 2 years younger than smith is.
j = s - 2
In 5 years, john will be twice as old as smith is now.
j + 5 = 2s
Replace j with (s-2)
(s-2) + 5 = 2s
s + 3 = 2s
3 = 2s - s
s = 3 yrs old is Smith (John is 1)