SOLUTION: Joe is 5 years older than Sally. In 15 years Joe will be 3 times as old as Sally is now. How old is Sally now? Hint: Write Joe's age now in terms of Sally's age now. Then write Joe

Algebra ->  Finance -> SOLUTION: Joe is 5 years older than Sally. In 15 years Joe will be 3 times as old as Sally is now. How old is Sally now? Hint: Write Joe's age now in terms of Sally's age now. Then write Joe      Log On


   

Question 147898: Joe is 5 years older than Sally. In 15 years Joe will be 3 times as old as Sally is now. How old is Sally now? Hint: Write Joe's age now in terms of Sally's age now. Then write Joe's age in 15 years using the expression you just wrote for Joe's age now. Then using S for Sally's age now, write the equation with only one variable "S" and solve it.
I need help with this :)
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Joe's age is J.
Sally's age is S.
Joe is 5 years older than Sally.
1.J=5%2BS
In 15 years, Joe will be J+15.
In 15 years Joe will be 3 times as old as Sally is now.
2.J%2B15=3S
Substitute J from eq. 1 into eq. 2 to get an equation in S only,
2.J%2B15=3S
%285%2BS%29%2B15=3S
20%2BS=3S
20=2S
S=10
From eq. 1,
1.J=5%2BS
J=5%2B10
J=15