Question 795430: This year, Jake is 5 years older than his sister. Three years ago, Jake was twice his sister's age. How old is Jake's sister?
Answer by DrBeeee(684)   (Show Source):
You can put this solution on YOUR website! Let j = Jake's current age
Let s = his sisters current age
The first statement gives us
(1) j = s + 5
The second statement about 3 years ago we have
(2) j = 2*s, but this is 3 years ago , so we have
(3) j-3 = 2*(s-3) OK? or
(4) j = 2*s -6 +3 or
(5) j = 2*s -3
Now solve (1) and (5) simultaneously.
Since j = j we can set (1) = (5) to get
(6) s + 5 = 2*s - 3 or
(7) s = 8
From (1) we get
(8) j = 8 + 5 or
(9) j = 13
Let's check this using (3).
Is (13 - 3 = 2*(8 - 3))?
Is (10 = 2*5)?
Is (10 = 10)? Yes
Answer: This year Jake's sister is 8 years old.
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