SOLUTION: I need the process to solve this problem: Bob is one third the age of his father. In 12 years he will be half the age of his father. How old is each now?

Question 507100: I need the process to solve this problem:
Bob is one third the age of his father. In 12 years he will be half the age of his father. How old is each now?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
Let b = Bob's present age
Let f = Father's age
:
Write an equation for each statement:
:
"Bob is one third the age of his father."
b = f
or
f = 3b
:
"In 12 years he will be half the age of his father."
b + 12 = .5(f + 12)
b + 12 = .5f + 6
b = .5f + 6 - 12
b = .5f - 6
Replace f with 3b
b = .5(3b) - 6
b = 1.5b - 6
6 = 1.5b - b
6 = .5b
b = 12 yrs is Bob's present age
then
f = 3(12)
f = 36 is Dad's present age
;
:
See if that works out in the statement
"In 12 years he will be half the age of his father."
12 + 12 = .5(36 + 12)
24 = .5(48)
How old is each now?
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