SOLUTION: Jack is 17 years old and his sister is four years younger than he is. In how many years will the sum of their ages be triple what the sum of their ages is now?

Question 587382: Jack is 17 years old and his sister is four years younger than he is. In how many years will the sum of their ages be triple what the sum of their ages is now?
Found 2 solutions by richwmiller, lwsshak3:
Answer by richwmiller(17219) (Show Source): You can put this solution on YOUR website!
s=j-4
j=17
3*(j+s)=(j+s+2x)
j = 17, s = 13, x = 30
In 30 years their ages will add up to 90
now their ages add up to 30

Answer by lwsshak3(11628) (Show Source): You can put this solution on YOUR website!
Jack is 17 years old and his sister is four years younger than he is. In how many years will the sum of their ages be triple what the sum of their ages is now?
**
At present:
Jack is 17 years old
His sister is 13 years old
sum of their ages=30
..
x years from now:
Jack will be 17+x years old
His sister will be 13+x years old
..
3*30=17+x+13+x
90=30+2x
2x=60
x=30
ans:
Years the sum of their ages be triple what the sum of their ages is now=30

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