Question 846191
Let f = father's age
let s = son's age
:
Write an equation for each statement, smplify.
:
"Five years from now, a father's age will be three times his son's age,"
f + 5 = 3(s+5)
f + 5 = 3s + 15
f = 3s + 15 - 5
f = 3s + 10 
"and five years ago, he was seven times as old as his son was."
f - 5 = 7(s-5)
f - 5 = 7s - 35
f = 7s - 35 + 5
f = 7s - 30
Use this to replace f in the 1st equation
7s - 30 = 3s + 10
You should be able to solve this now. Check your solutions in both statements


 How do I set up this problem to solve as a system?