subtract
4 1/5 = /10 = 2/10
= 4 2/10 = 3 + 1 + 2/10 = 3 + 10/10 + 2/10
= 3 12/10
- 1 1/2 = /10 = 5/10 =
- 1 5/10 =
- 1 5/10
2 7/10
return