let age of anil be x

let age of his father be y

x+y=54, therefore, x=54-y---------equation 1

y-6=6(x-6)

substitute value of x from eq.1

y-6=6(54-y-6)

=6(48-y)

=288-6y

y+6y=288+6

7y=294

therefore y =42 years,

therefore x=54-y=54-42=12 years