Let x denote the years that pass. After x years, the man will be 67 + x years old and the son will be 29 + x years old. Then, the son will be exactly half of the man's age when:
29 + x = (1/2)(67 + x).

Multiplying both sides by 2 gives:
58 + 2x = 67 + x
==> x + 58 = 67
==> x = 9.

Therefore, the son will be exactly half as old as the man in 9 years.
(Note that the son will be 29 + 9 = 38 years old when the man is 67 + 9 = 76 years old.)

I hope this helps!

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