Ok, so 38 - 91 is like 91-38 and then just add a negative to it. For example 1 - 2 is like 2 - 1 then add a negative so 2-1 = 1 then add a negative so -1. So for your original equation 91-38 is 53, and then just add a negative sign to that and it is -53. Hope this Helps!
91 - 38 = 53
129
just subtract 100 by 38 DUH!
91
53 + 38 = 91
Subtract 38 from 79: 79-38 = 41
-44
10
129
91 - 53 = 38
You can subtract. 98 - 60 = 38, so 1:38
53 Dr. Chuck