You can
put this solution on YOUR website!Let the present age of Billy be 'x' and the present age of his father 'y'.
Since Billy's father is twice as old as Billy,so
y=2x
11 years ago:
Billy's age was x-11 years.
Billy's father's age was y-11 years.
Since father was thrice as old,therefore:
y-11=3*(x-11)
Substituting for y we get,
2x-11=3*(x-11)
2x-11=3x-33
x=22
Hence, Billy is 22 years old.
