Question 126225
Let him have lived for x years.
Then the equation would be:

(x/4)+ (x/3) + 7 + (1/2)[x - (x/4  + x/3  + 7)] + (x/6) = x

==> (1/2)[x + (x/4  + x/3  + 7)] + (x/6) = x

==> [x + (x/4  + x/3  + 7)] + (x/3) = 2x [multiplying throughout by 2]

==> 7 = 2x - x - x/4 - x/3 - x/3

==> 7 = x/12 [ on taking 12 as the common denominator for the right side ans simplifying]

==> 84 = x [ multiplying by 12 on both sides]

Thus he had lived for 84 years.

His year of birth = 1908
So his year of death = 1908 + 84
                     = 1992

Good luck!!!