Posted by Oscar on Tuesday, September 26, 2006 at 9:08pm.
FIve years ago Zack would have been three times older than his young brother but five years from now he will only be two times older than his brother. How old is his brother?
25
In other words let x= brothers age so:
3(x5)=2(x+5)
Then 3x15=2x+10
x=25
I thought it might help to see the process. Five years ago, his age would be X5. Five years from now, it will be X+5. Can you see how we develop the formula below?
3(X5) = 2(X+5)
Just multiply and solve for X.
I hope this helps a little more. Thanks for asking.
Did anyone even see that the question wanted his brother's age. Also, how did you test your answers?
Let y be Zack's age and x his brother's age. We're told
y5=3(x5)=3x15 so y=3x10
y+5=2(x+5)=2x+10 so y=2x+5
equating them
3x10=2x+5, and solving for x we find his brother is 15 and Zack is 35.
Test: 5yrs ago Zack was 30 and his brother was 10. 5yrs from now Zack is 40 and his brother is 20.

Math  j.hargrove, Wednesday, November 4, 2009 at 7:12pm
y=3x10
y=2x5
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