Record subtraction with renaming 12/3/10-7/7/10 =

First what re write the problem:
12/3/10-7/7/10
12/3 = 4
4/10-7/7
4/10 = .4
.4-7/7/10
7/7 = 1
.4-1/10
1/10 = .1
so our final problem is this:
.4-.1
.3  
Hope this helped!