Question

Kathy is 6 years younger the Bill. Twelve years ago, Bill was twice as old as kathy was then. How old are they now?

Answer 1

k = Kathy's age now
 b= Bill's age now
(1) k=b-6
(2) b-12=2 x (k-12)
(2) b-12=2k-24
(2) 2k-b=12
From (1)
(1) -k+b=12
Add (1) and (2)
k=18
and
(1) k=b-6
18=b-6
b=24
Kathy is 18 and Bill is 24
check:
(2) b-12=2 x )k-12)
24-12=2 x (18-12) 
12=12
OK