First you do 120$-48$=
1. H T U - so that you don't get confused when subtracting.
2. Layout - you need to layout your work out like this:
H T U
1 2 0
- 4 8
-------------------
0 7 2
-------------------
So that mean 72% of the bill was for labour
Hope this helped you!
:) :) :) :)