Subtract till 100

Calculate:

The number of examples:
Numerical difficulty:
Range of values:
Multiplicity:

26	-	6	=
78	-	3	=
21	-	20	=
87	-	20	=
94	-	16	=
65	-	22	=
79	-	49	=
52	-	29	=
82	-	13	=
85	-	19	=