use timeline and work from NOW
me. mom
(1) @born 0. 27
My mum was 27 when I was born.
(2) now-8. x-8. y-8
(3) now. x y
(4) now+5. x+5. y+5
(1)&(3). y-x = 27-0 = 27
8 years ago she was twice as old as I shall be in 5 years time.
(2)&(4). y-8 = 2(x+5)
2 variables 2 equations ... solve x
x = 9, y = 36
