SOLUTION: Five years ago a man was seven times as old as his son. Five years hence, the father will be three times as old as his son. Find their present ages.

Algebra ->  Coordinate Systems and Linear Equations -> SOLUTION: Five years ago a man was seven times as old as his son. Five years hence, the father will be three times as old as his son. Find their present ages.      Log On


   

Question 154191: Five years ago a man was seven times as old as his son. Five years hence, the father will be three times as old as his son. Find their present ages.
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let f= father's age now
Let s= son's age now
f+-+5= father's age 5 years ago
s+-+5= son's age 5 years ago
f+-+5+=+7%2A%28s+-+5%29
f+-+5+=+7s+-+35
f+=+7s+-+30
------------------
f+%2B+5= father's age in 5 years hence
s+%2B+5= son's age in 5 years hence
f+%2B+5+=+3%2A%28s+%2B+5%29
f+%2B+5+=+3s+%2B+15
f+=+3s+%2B+10
-----------------
Set the 2 expressions for f equal to eachother
7s+-+30+=+3s+%2B+10
4s+=+40
s+=+10
Now substitute this in one of the equations
f+=+7s+-+30
f+=+7%2A10+-+30
f+=+40
The father is 40 and the son is 10