Question 573560
Let
age of Bill now = b
age of Father now = f


Billy’s father is now twice as old as Billy
f=2b..............(1)


Let x years ago
Bill was 
b-x = 14..............(2)
Father was 
f-x = 42..............(3)


Put the value of f from (1) to (3)
f-x = 42..............(3)
2b-x=42...............(4)
Subtract (2) from (4)
2b-x=42...............(4)
-b+x = -14..............(2)
-----------
b=28
Put the value of b in (1)
f=2b..............(1)
f=2(28)
f=56



age of Bill now = b = 28 years old
age of Father now = f = 56 years old