.
You can easily solve it MENTALLY in your head, without using equation/equations.
(1) In 9 years the sum of their ages will be 100 ---- hence, now the sum of their ages is 100-2*9 = 100-18 = 82.
(2) Cary is 6 years older than Dan and the sum of their ages is 82.
Take half of 82, which is 41, and SUBTRACT half of 6, i.e. 3, from 41 --- you will get 41-3 = 38 years.
It is the age of the younger men, Dan.
Take half of 82 again, which is 41, and ADD half of 6, i.e. 3, to it --- you will get 41+3 = 44 years.
It is the age of the older men, Cary.
Solved.