.
The problem says
x - 5 = .
It implies
2*(x-5) = x
2x - 10 = x
2x - x = 10
x = 10.
ANSWER. John is 10 years old.
Solved.
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There is a bunch of lessons on age word problems in this site:
- Age problems and their solutions
- A fresh formulation of a traditional age problem
- Really intricate age word problems
- Selected age word problems from the archive
- Age problems for mental solution
- One unusual age word problem
- Miscellaneous age problems
Read them attentively and become an expert in this field.