Question 492089
Let 
x=Current age of Ian
y=Current age of Brother

x+y=45
x=45-y.........(1)
In five years means we have to add 5 years in both ages, then Ian age will be five-sixths of his brother

x+5=(y+5)(5/6)
Multiply by 6 both sides
6(x+5)=(y+5)(5)
6x+30=5y+25
6x=5y+25-30
6x=5y-5.........(2)
Put the value of x from (1) to (2)
6(45-y)=5y-5
270-6y=5y-5
270+5=5y+6y
275=11y
y=275/11
y=25
Put the value of y in (1)
x=45-y.........(1)
x=45-25
x=20

Ian is 20 and his brother is 25 years old