Math

What you want to do is to make the fractions the same:

2 9ths = 12 54ths
1 6th = 9 54ths

So then you have 8 & 12 54ths - 1 & 9 54ths = (8-1 ) 7 + (12-9) 3 54ths.

now 3 54ths is the same as 1 18ths.

ANSWER: 7 & 3 18ths