Question 774175: The Johnson family has three sons, Billy, Tommy and Bobby. Billy is as old as Tommy and Bobby together. Last year, Tommy was twice as old as Bobby was. In two years, Billy will be twice as old as Tommy is now. How old is each son?
Answer by lwsshak3(11628)   (Show Source):
You can put this solution on YOUR website! The Johnson family has three sons, Billy, Tommy and Bobby. Billy is as old as Tommy and Bobby together. Last year, Tommy was twice as old as Bobby was. In two years, Billy will be twice as old as Tommy is now. How old is each son?
***
let x=tommy's present age
let y=bobby's present age
x+y=billy's present age
..
last year:
x-1=tommy's age
y-1=bobby's age
x+y-1=billy's age
tommy was twice as old bobby
x-1=2(y-1)
..
in 2 years:
x+2=tommy's age
y+2=bobby's age
x+y+2=billy's age
Billy will be twice as old as Tommy is now.
x+y+2=2x
..
x-1=2(y-1)
x+y+2=2x
..
x-1=2y-2
x+y+2=2x
..
x-2y=-1
x-y=2
-y=-3
y=3
x=2+y=5
x+y=8
tommy's present age=5
bobby's present age=3
billy's present age=8
|
|
|
