SOLUTION: John asked Jack how old he is. Jack replied: I am twice as old as you were when I was your age; when you are my age, our ages together will be 63. How old is each of them?

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Question 1068792: John asked Jack how old he is. Jack replied: I am twice as old as you were when I was your age; when you are my age, our ages together will be 63. How old is each of them?
Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
x= John's age (in years)
y= Jack's age (in years),
and we assume no tricks, as if both had birthdays on the same day.
Jack uses the phrase "when I was your age," implying that y%3Ex ,
but we know that the difference in ages is y-x years.
So, y-x years ago, Jack was Jon's age, and
John was y-x years younger than he is now, so his age was
x-%28y-x%29=x-y%2Bx=2x-y .
Jack says he is twice as old as that, so
y=2%282x-y%29<--->y=4x-2y<--->highlight%283y=4x%29 .
Jack says "when you are my age, our ages together will be 63."
That is in the future, y-x years into the future,
since that is the difference in their ages.
At that point,
John's age will be y (Jack's current age), and
Jack's age will be
y%2B%28y-x%29=2y-x .
The sum of their ages at that point will be
y%2B%282y-x%29=63 <--->highlight%283y-x=63%29 .
We have a system of 2 linear equations with 2 variables to solve.
There are many ways to go from initial set of equations to solutions.
Here is the scenic zig-zaggy way:
system%283y=4x%2C3y-x=63%29-->system%283y=4x%2C4x-x=63%29-->system%283y=4x%2C3x=63%29-->system%28y=4x%2F3%2C3x=63%29-->system%28y=4x%2F3%2Cx=63%2F3%29-->system%28y=4x%2F3%2Cx=21%29-->system%28y=4%2A21%2F3%2Cx=21%29-->highlight%28system%28y=28%2Cx=21%29%29