Sharon is 10
Brian is 5
In five years, they will both be 5 years older, so they will be a combined 10 years older. If you subtract 10 years from 25, that means that right now their ages add up to 15. If Sharon is twice as old as Brian, than her age is made up of 2/3 of the remaining 15 years, and Brian's age is 1/3 of the remaining 15. That means Sharon is 10 and Brian is 5.
If math is needed:
Sharon = x
Brian = y
x = 2y
(x + 5 years) + (y + 5 years) = 25 years
x + 5 + y + 5 = 25
x + y + 10 = 25
x + y = 15
(substitute "x" with "2y")
x + y = 15
(2y) + y = 15
3y = 15
y = 5 ( Brian is 5)
use y value to find x
x = 2y
x = 2(5)
x = 10 ( Sharon is 10)
