Adam is 3 times as old as Cynthia and Fred is 16 years younger than adam. One year ago, Adam's age was twice the sum of Cythia and Freds age. Find the present ages.

Question

I have
a=3c f=a-16 a-1=2(c-1 + f-1)

and I don't understand what comes next and why

Answer 1

a=3c
f=a-16
a-1=2(c-1 + f-1)

so far, so good. Now start substituting. First, get rid of a:

f = 3c-16
3c-1 = 2(f+c-2)

Now get rid of the f:

3c-1 = 2((3c-16)+c-2)
3c-1 = 2(4c-18)
3c-1 = 8c - 36
5c = 35
c = 7
so, f = 3c-16 = 5
and a = 3c = 21