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Let's translate your homework to equations.
First equation is
F = , or, which is the same, 3F = S. (1)
Second equation is
F + 12 = , which is the same as 2*(F+12) = S + 12. (2)
At this moment you must make an effort and get understanding what is F+12 at the left side, and what is S+12 at the right side.
As soon as you understand it, you will easily solve ANY age word problem.
So, from the condition, you have this system of two equations
3F = S, (1) and
2*(F+12) = S + 12. (2)
Simplify (2)
2F + 24 = S + 12
and substitute 3F instead of S into this equation, based on (1). You will get a single equation for F:
2F + 24 = 3F + 12 ====> F = 24 - 12 = 12.
Answer. Fran is 12 years old. Stan is 3*12 = 36 years old.
Solved.
There is a bunch of lessons on age word problems
- Age problems and their solutions
- A fresh formulation of a traditional age problem
- Really intricate age word problem
- Selected age word problems from the archive
- Age problems for mental solution
in this site.
Read them and become an expert in solving age problems.
Also, you have this free of charge online textbook in ALGEBRA-I in this site
- ALGEBRA-I - YOUR ONLINE TEXTBOOK.
The referred lessons are the part of this online textbook under the topic "Age word problems".