SOLUTION: Barry is 8 years older than his sister in three years he will be twice as old as she is then. How old are they?

Question 514201: Barry is 8 years older than his sister in three years he will be twice as old as she is then. How old are they?
Answer by Maths68(1474) (Show Source): You can put this solution on YOUR website!
Let
Present age of Barry = b
Present age of Sister = s
Barry is 8 years older than his sister
b=s+8........(1)
In three years
b+3=s+3
He will be twice as old as his son
b+3=2(s+3)
b+3=2s+6
b=2s+6-3
b=2s+3
Subtitute the value of m from (1) to (2)
s+8=2s+3
s=2s+3-8
s-2s=-5
-s=-5
Multiply by (-1) both sides
(-1)(-b)=(-1)(-5)
s=5
Put the value of b in (1)
b=s+8
b=5+8
b=13
Present age of Barry = b = 13
Present age of Sister = s = 5
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