Question 671717
let father be x
son be y
x=2y

12 years ago
father's age = x-12
son's age y-12

(x-12) = 4(y-12)

but x=2y

(2y-12)=4(y-12)

2y-12=4y-48
2y-4y=-48+12
-2y=-36
y=-36/-2
y=18 son's age

x= 2y
x=36 father's age