A, B, C and D are celebrating their joint birthdays and find
that their ages add up to exactly 100 years. The sum of A's and
D's ages equals the sum of B and C, while the difference between
the ages of A and D is twice C's age. Finally when D is as old
as A is now, C will be twice as old as B is now.
Given that A is older than D, how old are the four of them?
I constructed the following but I am unsure if they are correct, and where I would go from there?
a+b+c+d = 100
a+d = b+c
a-d = 2c
a > d
when... d = a
2c = b
Any help greatly appreciated, thanks