When you solve a problem with fractions, you want them to have a common denominator. You can change 6 to 5 12/12, because 12/12 is the same as 1. Then you set up your problem.
5 12/12
- 1 5/12 First, you subtract the whole numbers, so 5 -1. Then, -------------- the numerators of the fractions.
4 7/12